bluuebunny/crossref_metadata_2025 huggingface dataset:
Calretinin and calbindin D28k have different domain organizations
Authors: Palczewska Małgorzata , Groves Patrick , Batta Gyula , Heise Bert , Kuźnicki Jacek
Published: August 2003

The domain organization of calretinin (CR) was predicted to involve all six EF‐hand motifs (labeled I to VI) condensed into a single domain, as characterized for calbindin D28k (Calb), the closest homolog of calretinin. Unperturbed1H,15N HSQC NMR spectra of a15N‐labeled calretinin fragment (CR III–VI, residues 100–271) in the presence of the unlabeled complimentary fragment (CR I–II, residues 1–100) show that these fragments do not interact. Size exclusion chromatography and affinity chromatography data support this conclusion. The HSQC spectrum of15N‐labeled CR is similar to the overlaid spectra of individual15N‐labeled CR fragments (CR I–II and CR III–VI), also suggesting that these regions do not interact within intact CR. In contrast to these observations, but in accordance with the Calb studies, we observed interactions between other CR fragments: CR I (1–60) with CR II–VI (61–271), and CR I–III (1–142) with CR IV–VI (145–271). We conclude that CR is formed from at least two independent domains consisting of CR I–II and CR III–VI. The differences in domain organization of Calb and CR may explain the specific target interaction of Calb with caspase‐3. Most importantly, the comparison of CR and Calb domain organizations questions the value of homologous modeling of EF‐hand proteins, and perhaps of other protein families.
Screening for functional expression and overexpression of a family of diiron‐containing interfacial membrane proteins using the univector recombination system
Authors: Berthold Deborah A. , Stenmark Pål , Nordlund Pär
Published: August 2003

The large number of uncharacterized genes emerging from genome sequencing projects has resulted in a need for quick and reliable screening methods for protein expression parameters. We have utilized the univector plasmid recombination system (as previously reported) to develop a series of vectors for rapid screening for expression in Escherichia coli. A high level of recombinant protein expression is a requirement for purification of protein for structural determination and other purposes. In other applications, successful complementation of a missing enzyme activity in E. coli, as well as directed evolution studies and metabolic engineering, often require a much lower level of protein expression. In this report we describe the construction of a number of new pHOST vectors that can be screened for both low‐ and high‐level expression. We isolated a mutant vector for MBP fusions that exhibited a more optimal level of expression for complementation of aerobic respiration in hemA− E. coli, our functional assay for the alternative oxidase. We then demonstrated the use of our system to rapidly screen for both optimal functional expression and optimal overexpression of the alternative oxidase as well as two other members of a family of membrane‐bound diiron carboxylate proteins, the plastid terminal oxidase and 5‐demethoxyquinone hydroxylase.
Position‐dependent interactions between cysteine residues and the helix dipole
Authors: Miranda JJ L.
Published: August 2003

A protein model was developed for studying the interaction between cysteine residues and the helix dipole. Site‐directed mutagenesis was used to introduce cysteine residues at the N‐terminus of helix H in recombinant sperm whale myoglobin. Based on the difference in thiol pKa between folded proteins and an unfolded peptide, the energy of interaction between the thiolate and the helix dipole was determined. Thiolates at the N1 and N2 positions of the helix were stabilized by 0.3 kcal/mole and 0.7 kcal/mole, respectively. A thiolate at the Ncap position was stabilized by 2.8 kcal/mole, and may involve a hydrogen bond. In context with other studies, an experimentally observed helix dipole effect may be defined in terms of two distinct components. A charge‐dipole component involves electrostatic interactions with peptide bond dipoles in the first two turns of the helix and affects residues at all positions of the terminus; a hydrogen bond component involves one or more backbone amide groups and is only possible at the capping position due to conformational restraints elsewhere. The nature and magnitude of the helix dipole effect is, therefore, position‐dependent. Results from this model system were used to interpret cysteine reactivity in rodent hemoglobins and the thioredoxin family.
NMR detection of multiple transitions to low‐populated states in azurin
Authors: Korzhnev Dmitry M. , Karlsson B. Göran , Orekhov Vladislav Yu. , Billeter Martin
Published: August 2003

Transitions to conformational states with very low populations were detected for the reduced blue copper protein azurin from Pseudomonas aeruginosa by applying constant relaxation time CPMG measurements to the backbone 15N nuclei at three magnetic fields (11.7, 14.1, and 18.8 T) and three temperatures (25.7, 35.4, and 44.8°C). Two exchange processes with different rate constants could be discriminated despite populations of the excited states below 1% and spatial neighborhood of the two processes. The group of 15N nuclei involved in the faster process exhibits at 44.8°C a forward rate constant of 11.7±2.4 s−1 and a population of the exited state of 0.39±0.07%. They surround the aromatic ring of histidine 35 whose protonation state is coupled to the flipping of a neighboring peptide plane. For the slower process, the forward rate constant and population of the exited state at 44.8°C are 4.1±0.1 s−1 and 0.45±0.02%, respectively. The residues involved cluster nearby the copper ion, which is separated from the protonation site of histidine 35 by about 8 Å, indicating conformational rearrangements involving the copper coordinating loops. The dependence of the equilibrium constant on the temperature is consistent with an enthalpy‐dominated transition around the copper, but an entropy‐controlled transition near histidine 35. The detection by nuclear magnetic resonance of millisecond to second conformational transitions near the copper ion suggests a low energy‐cost rearrangement of the copper‐binding site that may be necessary for efficient electron transfer.
Leucine 145 of the ribotoxin α‐sarcin plays a key role for determining the specificity of the ribosome‐inactivating activity of the protein
Authors: Masip Manuel , García‐Ortega Lucía , Olmo Nieves , García‐Mayoral Ma Flor , Pérez‐Cañadillas José Manuel , Bruix Marta , Oñaderra Mercedes , Martínez del Pozo Álvaro , Gavilanes José G.
Published: August 2003

Secreted fungal RNases, represented by RNase T1, constitute a family of structurally related proteins that includes ribotoxins such as α‐sarcin. The active site residues of RNase T1 are conserved in all fungal RNases, except for Phe 100 that is not present in the ribotoxins, in which Leu 145 occupies the equivalent position. The mutant Leu145Phe of α‐sarcin has been recombinantly produced and characterized by spectroscopic methods (circular dichroism, fluorescence spectroscopy, and NMR). These analyses have revealed that the mutant protein retained the overall conformation of the wild‐type α‐sarcin. According to the analyses performed, Leu 145 was shown to be essential to preserve the electrostatic environment of the active site that is required to maintain the anomalous low pKa value reported for the catalytic His 137 of α‐sarcin. Enzymatic characterization of the mutant protein has revealed that Leu 145 is crucial for the specific activity of α‐sarcin on ribosomes.
Structural genomics: Computational methods for structure analysis
Authors: Goldsmith‐Fischman Sharon , Honig Barry
Published: August 2003

The success of structural genomics initiatives requires the development and application of tools for structure analysis, prediction, and annotation. In this paper we review recent developments in these areas; specifically structure alignment, the detection of remote homologs and analogs, homology modeling and the use of structures to predict function. We also discuss various rationales for structural genomics initiatives. These include the structure‐based clustering of sequence space and genome‐wide function assignment. It is also argued that structural genomics can be integrated into more traditional biological research if specific biological questions are included in target selection strategies.
Contact order revisited: Influence of protein size on the folding rate
Authors: Ivankov Dmitry N. , Garbuzynskiy Sergiy O. , Alm Eric , Plaxco Kevin W. , Baker David , Finkelstein Alexei V.
Published: August 2003

Guided by the recent success of empirical model predicting the folding rates of small two‐state folding proteins from the relative contact order (CO) of their native structures, by a theoretical model of protein folding that predicts that logarithm of the folding rate decreases with the protein chain length L as L2/3, and by the finding that the folding rates of multistate folding proteins strongly correlate with their sizes and have very bad correlation with CO, we reexamined the dependence of folding rate on CO and L in attempt to find a structural parameter that determines folding rates for the totality of proteins. We show that the Abs_CO = CO × L, is able to predict rather accurately folding rates for both two‐state and multistate folding proteins, as well as short peptides, and that this Abs_CO scales with the protein chain length as L0.70 ± 0.07 for the totality of studied single‐domain proteins and peptides.
Structural signatures of the complex formed between 3‐nitro‐4‐hydroxybenzoate and the Zn(II)‐substituted R6 insulin hexamer
Authors: Olsen Helle Birk , Leuenberger‐Fisher Melissa R. , Kadima Webe , Borchardt Dan , Kaarsholm Niels C. , Dunn Michael F.
Published: August 2003

3‐Nitro‐4‐hydroxybenzoate (3N4H) is a probe of the structure and dynamics of the metal‐centered His B10 assembly sites of the insulin hexamer. Each His B10 site consists of a ∼12 Å‐long cavity situated on the threefold symmetry axis. These sites play an important role in the storage and release of insulin in vivo. The allosteric behavior of the insulin hexamer is modulated by ligand binding to the His B10 zinc sites and to the phenolic pockets. Binding to these sites drives transitions among three allosteric states, designated T6, T3R3, and R6. Although a wide variety of mono anions bind to the His B10 zinc sites of R3, X‐ray structures of ligands complexed to this site exist only for H2O, Cl–, and SCN–. This work combines one‐ and two‐dimensional 1H NMR and UV‐Vis absorbance studies of the structure and dynamics of the 3N4H complex, which establish the following: (1) relative to the NMR time scale, 3N4H exchange between free and bound states is slow, while flipping among three equivalent orientations about the site threefold axis is fast; (2) binding of 3N4H perturbs resonances within the His B10 zinc site and generates NOEs between ligand resonances and the insulin C‐α and side chain resonances of ValB2, AsnB3, LeuB6, and CysB7; and (3) 3N4H exchange for other ligands is limited by a protein conformational transition. These results are consistent with coordination of the 3N4H carboxylate to the His B10 zinc ion and van der Waals interactions with Val B2, Asn B3, Leu B6, and Cys A7.
Structure–activity relationships in HIV‐1 reverse transcriptase revealed by radiation target analysis
Authors: Sluis‐Cremer Nicolas , Kempner Ellis , Parniak Michael A.
Published: August 2003

Radiation target analysis is a powerful technique that can be used to determine both the structural and functional sizes of macromolecules. We have used this technique to probe the structure–function relationships of the recombinant forms of HIV‐1 reverse transcriptase (RT). For the p66/p51 and p66/p66 dimeric forms of HIV‐1 RT, both the structural and functional target sizes corresponded to that of the dimeric protein, indicating that a primary ionization in one subunit of the HIV‐1 RT enzyme results in the concomitant polymer scission of both subunits. In contrast to p66/p51 and p66/p66 RT, the individually isolated p51 subunit of HIV‐1 RT inactivated as a monomer. However, in the presence of a DNA template/primer substrate, the radiation inactivation analyses of p51 yielded a structural target size corresponding to that of a dimeric protein. This would indicate that the DNA substrate acted as a scaffold or template for p51 RT homodimer formation. In light of this observation, radiation inactivation studies can readily be applied to other DNA polymerase enzymes, such as the murine leukemia virus RT, for which the functional form of the enzyme has yet to be determined.
Site2 binding energetics of the regulatory step of growth hormone–induced receptor homodimerization
Authors: Walsh Scott T.R. , Jevitts Liz M. , Sylvester Juliesta E. , Kossiakoff Anthony A.
Published: August 2003

Receptor signaling in the growth hormone (GH)–growth hormone receptor (GHR) system is controlled through a sequential two‐step hormone‐induced dimerization of two copies of the extracellular domain (ECD) of the receptor. The regulatory step of this process is the binding of the second ECD (ECD2) to the stable preassociated 1 : 1 GH/ECD1 complex on the cell surface. To determine the energetics that governs this step, the binding kinetics of 38 single‐ and double‐alanine mutants in the hGH Site2 contact with ECD2 were measured by using trimolecular surface plasmon resonance (TM‐SPR). We find that the Site2 interface of hGH does not have a distinct binding hot‐spot region, and the most important residues are not spatially clustered, but rather are distributed over the whole binding surface. In addition, it was determined through analysis of a set of pairwise double alanine mutations that there is a significant degree of negative cooperativity among Site2 residues. Residues that show little effect or even improved binding on substitution with alanine, when paired with D116A‐hGH, display significant negative cooperativity. Because most of these pairwise mutated residues are spatially separated by ≥10 Å, this indicates that the Site2 binding interface of the hGH–hGHR ternary complex displays both structural and energetic malleability.
Crystal structure of mycothiol synthase (Rv0819) from Mycobacterium tuberculosis shows structural homology to the GNAT family of N‐acetyltransferases
Authors: Vetting Matthew W. , Roderick Steven L. , Yu Michael , Blanchard John S.
Published: August 2003

Mycothiol is the predominant low‐molecular weight thiol produced by actinomycetes, including Mycobacterium tuberculosis. The last reaction in the biosynthetic pathway for mycothiol is catalyzed by mycothiol synthase (MshD), which acetylates the cysteinyl amine of cysteine–glucosamine–inositol (Cys–GlcN–Ins). The crystal structure of MshD was determined in the presence of coenzyme A and acetyl–CoA. MshD consists of two tandem‐repeated domains, each exhibiting the Gcn5‐related N‐acetyltransferase (GNAT) fold. These two domains superimpose with a root‐mean‐square deviation of 1.7 Å over 88 residues, and each was found to bind one molecule of coenzyme, although the binding sites are quite different. The C‐terminal domain has a similar active site to many GNAT members in which the acetyl group of the coenzyme is presented to an open active site slot. However, acetyl–CoA bound to the N‐terminal domain is buried, and is apparently not positioned to promote acetyl transfer. A modeled substrate complex indicates that Cys–GlcN–Ins would only fill a portion of a negatively charged channel located between the two domains. This is the first structure determined for an enzyme involved in the biosynthesis of mycothiol.
Dissecting interdomain communication within cAPK regulatory subunit type IIβ using enhanced amide hydrogen/deuterium exchange mass spectrometry (DXMS)
Authors: Zawadzki Kerri M. , Hamuro Yoshitomo , Kim Jack S. , Garrod Siv , Stranz David D. , Taylor Susan S. , Woods Virgil L.
Published: August 2003

cAMP‐dependent protein kinase (cAPK) is a heterotetramer containing a regulatory (R) subunit dimer bound to two catalytic (C) subunits and is involved in numerous cell signaling pathways. The C‐subunit is activated allosterically when two cAMP molecules bind sequentially to the cAMP‐binding domains, designated A and B (cAB‐A and cAB‐B, respectively). Each cAMP‐binding domain contains a conserved Arg residue that is critical for high‐affinity cAMP binding. Replacement of this Arg with Lys affects cAMP affinity, the structural integrity of the cAMP‐binding domains, and cAPK activation. To better understand the local and long‐range effects that the Arg‐to‐Lys mutation has on the dynamic properties of the R‐subunit, the amide hydrogen/deuterium exchange in the RIIβ subunit was probed by electrospray mass spectrometry. Mutant proteins containing the Arg‐to‐Lys substitution in either cAMP‐binding domain were deuterated for various times and then, prior to mass spectrometry analysis, subjected to pepsin digestion to localize the deuterium incorporation. Mutation of this Arg in cAB‐A (Arg230) causes an increase in amide hydrogen exchange throughout the mutated domain that is beyond the modest and localized effects of cAMP removal and is indicative of the importance of this Arg in domain organization. Mutation of Arg359 (cAB‐B) leads to increased exchange in the adjacent cAB‐A domain, particularly in the cAB‐A domain C‐helix that lies on top of the cAB‐B domain and is believed to be functionally linked to the cAB‐B domain. This interdomain communication appears to be a unidirectional pathway, as mutation of Arg230 in cAB‐A does not effect dynamics of the cAB‐B domain.
Structure of the Escherichia coli malate synthase G:pyruvate:acetyl‐coenzyme A abortive ternary complex at 1.95 Å resolution
Authors: Anstrom David M. , Kallio Karen , Remington S. James
Published: August 2003

Malate synthase, an enzyme of the glyoxylate pathway, catalyzes the condensation and subsequent hydrolysis of acetyl‐coenzyme A (acetyl‐CoA) and glyoxylate to form malate and CoA. In the present study, we present the 1.95 Å–resolution crystal structure of Escherichia coli malate synthase isoform G in complex with magnesium, pyruvate, and acetyl‐CoA, and we compare it with previously determined structures of substrate and product complexes. The results reveal how the enzyme recognizes and activates the substrate acetyl‐CoA, as well as conformational changes associated with substrate binding, which may be important for catalysis. On the basis of these results and mutagenesis of active site residues, Asp 631 and Arg 338 are proposed to act in concert to form the enolate anion of acetyl‐CoA in the rate‐limiting step. The highly conserved Cys 617, which is immediately adjacent to the presumed catalytic base Asp 631, appears to be oxidized to cysteine‐sulfenic acid. This can explain earlier observations of the susceptibility of the enzyme to inactivation and aggregation upon X‐ray irradiation and indicates that cysteine oxidation may play a role in redox regulation of malate synthase activity in vivo. There is mounting evidence that enzymes of the glyoxylate pathway are virulence factors in several pathogenic organisms, notably Mycobacterium tuberculosis and Candida albicans. The results described in this study add insight into the mechanism of catalysis and may be useful for the design of inhibitory compounds as possible antimicrobial agents.
Solution structure of Pi4, a short four‐disulfide‐bridged scorpion toxin specific of potassium channels
Authors: Guijarro J. Iñaki , M'Barek Sarrah , Gómez‐Lagunas Froylan , Garnier Damien , Rochat Hervé , Sabatier Jean‐Marc , Possani Lourrival D. , Delepierre Muriel
Published: August 2003

Pi4 is a short toxin found at very low abundance in the venom of Pandinus imperator scorpions. It is a potent blocker of K+ channels. Like the other members of the α‐KTX6 subfamily to which it belongs, it is cross‐linked by four disulfide bonds. The synthetic analog (sPi4) and the natural toxin (nPi4) have been obtained by solid‐phase synthesis or from scorpion venom, respectively. Analysis of two‐dimensional 1H NMR spectra of nPi4 and sPi4 indicates that both peptides have the same structure. Moreover, electrophysiological recordings of the blocking of Shaker B K+ channels by sPi4 (KD = 8.5 nM) indicate that sPi4 has the same blocking activity of nPi4 (KD = 8.0 nM), previously described. The disulfide bonds have been independently determined by NMR and structure calculations, and by Edman‐degradation/mass‐spectrometry identification of peptides obtained by proteolysis of nPi4. Both approaches indicate that the pairing of the half‐cystines is 6C–27C, 12C–32C, 16C–34C, and 22C–37C. The structure of the toxin has been determined by using 705 constraints derived from NMR data on sPi4. The structure, which is well defined, shows the characteristic α/β scaffold of scorpion toxins. It is compared to the structure of the other α‐KTX6 subfamily members and, in particular, to the structure of maurotoxin, which shows a different pattern of disulfide bridges despite its high degree of sequence identity (76%) with Pi4. The structure of Pi4 and the high amounts of synthetic peptide available, will enable the detailed analysis of the interaction of Pi4 with K+ channels.
Phosphohydrolase and transphosphatidylation reactions of two Streptomyces phospholipase D enzymes: Covalent versus noncovalent catalysis
Authors: Yang Hongying , Roberts Mary F.
Published: August 2003

A kinetic comparison of the hydrolase and transferase activities of two bacterial phospholipase D (PLD) enzymes with little sequence homology provides insights into mechanistic differences and also the more general role of Ca2+ in modulating PLD reactions. Although the two PLDs exhibit similar substrate specificity (phosphatidylcholine preferred), sensitivity to substrate aggregation or Ca2+, and pH optima are quite distinct. Streptomyces sp. PMF PLD, a member of the PLD superfamily, generates both hydrolase and transferase products in parallel, consistent with a mechanism that proceeds through a covalent phosphatidylhistidyl intermediate where the rate‐limiting step is formation of the covalent intermediate. For Streptomyces chromofuscus PLD, the two reactions exhibit different pH profiles, a result consistent with a mechanism likely to involve direct attack of water or an alcohol on the phosphorus. Ca2+, not required for monomer or micelle hydrolysis, can activate both PLDs for hydrolysis of PC unilamellar vesicles. In the case of Streptomyces sp. PMF PLD, Ca2+ relieves product inhibition by interactions with the phosphatidic acid (PA). A similar rate enhancement could occur with other HxKx4D‐motif PLDs as well. For S. chromofuscus PLD, Ca2+ is absolutely critical for binding of the enzyme to PC vesicles and for PA activation. That the Ca2+‐PA activation involves a discreet site on the protein is suggested by the observation that the identity of the C‐terminal residue in S. chromofuscus PLD can modulate the extent of product activation.
Molecular modeling of the membrane targeting of phospholipase C pleckstrin homology domains
Authors: Singh Shaneen M. , Murray Diana
Published: August 2003

Phospholipases C (PLCs) reversibly associate with membranes to hydrolyze phosphatidylinositol‐4, 5‐bisphosphate (PI[4,5]P2) and comprise four main classes: β, γ, δ, and ε. Most eukaryotic PLCs contain a single, N‐terminal pleckstrin homology (PH) domain, which is thought to play an important role in membrane targeting. The structure of a single PLC PH domain, that from PLCδ1, has been determined; this PH domain binds PI(4,5)P2 with high affinity and stereospecificity and has served as a paradigm for PH domain functionality. However, experimental studies demonstrate that PH domains from different PLC classes exhibit diverse modes of membrane interaction, reflecting the dissimilarity in their amino acid sequences. To elucidate the structural basis for their differential membrane‐binding specificities, we modeled the three‐dimensional structures of all mammalian PLC PH domains by using bioinformatic tools and calculated their biophysical properties by using continuum electrostatic approaches. Our computational analysis accounts for a large body of experimental data, provides predictions for those PH domains with unknown functions, and indicates functional roles for regions other than the canonical lipid‐binding site identified in the PLCδ1‐PH structure. In particular, our calculations predict that (1) members from each of the four PLC classes exhibit strikingly different electrostatic profiles than those ordinarily observed for PH domains in general, (2) nonspecific electrostatic interactions contribute to the membrane localization of PLCδ‐, PLCγ‐, and PLCβ‐PH domains, and (3) phosphorylation regulates the interaction of PLCβ‐PH with its effectors through electrostatic repulsion. Our molecular models for PH domains from all of the PLC classes clearly demonstrate how a common structural fold can serve as a scaffold for a wide range of surface features and biophysical properties that support distinctive functional roles.
Solution structure of the C‐terminal domain from poly(A)‐binding protein in Trypanosoma cruzi: A vegetal PABC domain
Authors: Siddiqui Nadeem , Kozlov Guennadi , D'Orso Iván , Trempe Jean‐François , Gehring Kalle
Published: August 2003

PABC is a phylogenetically conserved peptide‐binding domain primarily found within the C terminus of poly(A)‐binding proteins (PABPs). This domain recruits a series of translation factors including poly(A)‐interacting proteins (Paip1 and Paip2) and release factor 3 (RF3/GSPT) to the initiation complex on mRNA. Here, we determine the solution structure of the Trypanosoma cruzi PABC domain (TcPABC), a representative of the vegetal class of PABP proteins. TcPABC is similar to human PABC (hPABC) and consists of five α‐helices, in contrast to the four helices observed in PABC domains from yeast (yPABC) and hyper plastic disk proteins (hHYD). A mobile N‐terminal helix is observed in TcPABC that does not pack against the core of the protein, as found in hPABC. Characteristic to all PABC domains, the last four helices of TcPABC fold into a right‐handed super coil. TcPABC demonstrates high‐affinity binding to PABP interacting motif‐2 (PAM‐2) and reveals a peptide‐binding surface homologous to that of hPABC. Our results demonstrate the last four helices in TcPABC are sufficient for peptide recognition and we predict a similar binding mode in PABC domains. Furthermore, these results point to the presence of putative PAM‐2 site‐containing proteins in trypanosomes.
Intrinsic contributions of polar amino acid residues toward thermal stability of an ABC–ATPase of mesophilic origin
Authors: Sarin Jyoti , Raghava Gajendra P.S. , Chakraborti Pradip K.
Published: August 2003

The nucleotide‐binding subunit of phosphate‐specific transporter (PstB) from mesophilic bacterium, Mycobacterium tuberculosis, is a unique ATP‐binding cassette (ABC) ATPase because of its unusual ability to hydrolyze ATP at high temperature. In an attempt to define the basis of thermostability, we took a theoretical approach and compared amino acid composition of this protein to that of other PstBs from available bacterial genomes. Interestingly, based on the content of polar amino acids, this protein clustered with the thermophiles.
The accuracy of a river bed moulding/casting system and the effectiveness of a low‐cost digital camera for recording river bed fabric
Authors: Chandler Jim H. , Buffin‐Bélanger Tom , Rice Steve , Reid Ian , Graham David J.
Published: August 2003

Digital photogrammetry has been used to develop and test an artificial river bed moulding and casting system, which allows the pebbles within a coarse‐grain river bed to be recreated for hydraulic research in a laboratory flow channel or flume. Imagery of both the original streambed and the cast facsimile was acquired using a non‐metric Kodak DCS460 digital camera and digital elevation models and orthophotographs were derived and compared to assess the accuracy of the moulding and casting system. These comparative tests proved to be critical in modifying and developing the system.

Additional imagery was obtained in the field using a non‐metric Olympus C3030 ‘‘compact’’ digital camera to assess whether far cheaper camera technology could deliver data appropriate for such comparative examinations. Internal calibration parameter sets and data that were generated were compared with data obtained by the non‐metric Kodak DCS460. These tests demonstrate that digital sensors built around high‐quality 35 mm professional camera bodies and lenses are required for comparative examinations and for similar system development.
Photogrammetry in the Ordnance Survey from Close to MacLeod
Authors: Collier Peter , J. Inkpen Robert
Published: August 2003

In the period after the First World War the Ordnance Survey was relatively slow to recognise the contribution that air survey could make to its work. In part, this was due to external constraints on budgets, which helped to stifle innovation. However, the views of the four Directors General, Close, Jack, Winterbotham and MacLeod, were to play large roles in determining the energy with which innovations were adopted. Both Close and Winterbotham were generally sceptical about the value of air survey, while Jack was well disposed, but constrained by budget limitations. In MacLeod, however, air survey was to find a convinced champion. This paper explores the roles played by the key players and how, in the late 1930s, significant advances were made.
Autonomous space resection using Point‐ and Line‐Based representation of FREE‐FORM control Linear Features
Authors: Habib Ayman , Lin Hsiang Tseng , Morgan Michel
Published: August 2003

Automatic single photo resection (SPR) remains one of the challenging problems in digital photogrammetry. Visibility and uniqueness of distinct control points in the input imagery limit robust automation of the space resection procedure. Recent advances in photogrammetry mandate adopting higher‐level primitives, such as free‐form control linear features, for replacing traditional control points. Linear features can be automatically extracted from the image space. On the other hand, object space control linear features can be obtained from an existing GIS layer containing 3D vector data such as road networks or from newly developed terrestrial mobile mapping systems (MMS). In this paper, two different approaches are presented for simultaneously determining the position and attitude of the imagery as well as the correspondence between image and object space linear features. These approaches are based on two representation schemes of the linear features. The first one represents the linear feature by a sequence of 2D and 3D points along the linear feature in the image and object space, respectively. The second scheme assumes that the feature is modelled by polylines (a sequence of straight‐line segments). Neither approach requires one‐to‐one correspondence between image and object space primitives, which makes the suggested methodology robust against changes and/or discrepancies between the data‐sets involved. This characteristic will be helpful in detecting and dealing with changes between object and image space linear features (due to temporal effects for example). The parameter estimation and matching follow an optimal sequential procedure that is developed and described within this paper, which depends on the sensitivity of the mathematical model relating corresponding primitives at various image regions to incremental changes in the exterior orientation parameters (EOP). Experiments are conducted to compare the algorithms’ efficiency and the accuracy of the estimated EOP using both approaches. Experimental results using real data demonstrate the feasibility and robustness of both representation schemes as well as the methodologies developed. Moreover, different generalisation levels of the polylines representing the free‐form linear features are compared.
Geometric assessment of the kodak DCS Pro back
Authors: Mills Jon P. , Schneider Danilo , Barber David M. , Bryan Paul G.
Published: August 2003

This paper reports on an investigation into the suitability of the Kodak DCS Pro Back for use in close range photogrammetric measurement. The camera back, being used in conjunction with a medium‐format non‐metric camera, has been assessed with a view to using it for low‐ to medium‐order photogrammetric work in architectural recording. Examinations centred upon the stability of the camera back with respect to the camera body and the effects of the removable infrared filter that is present immediately above the camera's focal plane. Ultimately the camera combination was deemed suitable for application in recording of this kind and is now in active use by the Metric Survey Team at English Heritage.
Wage Effects of Drinking in Australia
Authors: Lee Yew Liang
Published: August 2003

This article analyses the wage effects of drinking using the Australian Twin Registry data. A multinomial logit framework is employed to explain the allocation of workers across various drinking states, and to correct for selection bias in the wage equations. It is found that there is a significant positive wage premium for moderate drinking. A favourable family background (during childhood) is positively related to the measure of moderate drinking. Greater genetic endowments are also associated with moderate drinking.
Inflation Expectations, Interest Rates and Arbitrary Income Transfers
Authors: Makin Tony
Published: August 2003

Unexpected inflation, disinflation or deflation cause arbitrary income transfers between an economy's borrowers and lenders. This redistribution results from distorted real interest rates that are too high when price level changes are over‐predicted and too low when they are under‐predicted. This article shows that in Australia's case, inflation expectations were mostly biased upwards throughout the 1990s, according to the Melbourne Institute of Applied Economic and Social Research series and to a new derived series based on bond yields, implying that real interest rates were too high over this time. In turn, this caused substantial arbitrary income transfers from debtors to creditors, estimated to have averaged up to 3 per cent of gross domestic product over the period.
Inflation Targeting as a Framework for Monetary Policy: A Cross‐Country Analysis
Authors: Seyfried William , Bremmer Dale
Published: August 2003

This study makes use of a dynamic Taylor‐type model to examine the conduct of monetary policy by central banks that profess to engage in inflation targeting. Previous research regarding inflation targeting and Taylor‐type rules is reviewed and a dynamic Taylor‐type model is developed. Tests for regime shifts upon the adoption of inflation targeting indicate a significant change in policy in each of the nations in the study for which sufficient data were available. Next, the central bank reaction functions were estimated. Results suggest that most of the central banks conducted a policy of inflation targeting by seeking to contain inflationary pressures rather than reacting to current inflation.
Estimating the Size of a Criminal Population from Police Records Using the Truncated Poisson Regression Model
Authors: Van Der Heijden Peter G.M. , Cruyff Maarten , Van Houwelingen Hans C.
Published: August 2003

The truncated Poisson regression model is used to arrive at point and interval estimates of the size of two offender populations, i.e. drunk drivers and persons who illegally possess firearms. The dependent capture–recapture variables are constructed from Dutch police records and are counts of individual arrests for both violations. The population size estimates are derived assuming that each count is a realization of a Poisson distribution, and that the Poisson parameters are related to covariates through the truncated Poisson regression model. These assumptions are discussed in detail, and the tenability of the second assumption is assessed by evaluating the marginal residuals and performing tests on overdispersion. For the firearms example, the second assumption seems to hold well, but for the drunk drivers example there is some overdispersion. It is concluded that the method is useful, provided it is used with care.
Latent Markov Modelling of Recidivism Data
Authors: Bijleveld Catrien C.J.H. , Mooijaart Ab
Published: August 2003

This article discusses the application of latent Markov modelling for the analysis of recidivism data. We briefly examine the relations of Markov modelling with log–linear analysis, pointing out pertinent differences as well. We show how the restrictive Markov model may be more easily applicable by adding latent variables to the model, in which case the latent Markov model is a dynamic version of the latent class model. As an illustration, we apply latent Markov analysis on an empirical data set of juvenile prosecution careers, showing how the Markov analyses producing well‐fitting and interpretable solutions. We end by comparing the possible contributions of Markov modelling in recidivism research, outlining its drawbacks as well. Recommendations and directions for future research conclude the article.
On the Market Failure in a Dixit‐Stiglitz Setup with Two Trading Cities
Authors: Hadar Yossi , Pines David
Published: August 2003

This study discusses the reasons for market failure and its bias in an economy with two cities and two final goods: tradeable differentiated products and non‐tradeable housing. It is shown that inside the city, as in Dixit and Stiglitz (1977), diversity (number of firms) is too small. With regard to the population partition between the cities, the paper distinguishes between a marginal and a global market bias against agglomeration or dispersion (in a second‐best context). The reasons for a marginal bias are twofold: a gap between marginal and average labor productivity and the (excessive) labor employed in housing production which vary between the large and the small cities. The source of the global bias is multiple stable equilibria. The marginal bias may be in an opposite direction to the global bias, such that more agglomeration may be marginally desirable, whereas full dispersion is (second‐best) optimal. Simulations demonstrate that the same market structure and potential source of market failure may imply bias in different directions, depending on the aggregate population size.
The Political Power of the Retirees in a Two‐Dimensional Voting Model
Authors: Casamatta Georges
Published: August 2003

We show that the retirees are able to obtain favorable pension policies whereas they belong to a minority in the population. The argument relies on the multidimensional nature of the political process. We consider a two‐dimensional collective choice problem. The first of these choices is the level of the contribution rate to the Pay‐As‐You‐Go pension system. The second is a noneconomic decision, unrelated to the pension system. Using a political agency model, we show that, as soon as the retirees are sufficiently numerous, the equilibrium tax rate may be higher than the tax rate preferred by the young, who yet constitute a majority over the pension issue.
Self‐financing Unemployment Insurance and Bargaining Structure
Authors: Sanner Helge
Published: August 2003

Abstract.  This study examines how the size of trade unions relative to the labor force impacts on the desirability of different organizational forms of self‐financing unemployment insurance (UI). For this purpose, we compare the outcome of a model with a uniform payroll tax to a model where workers pay taxes according to their systematic risk of unemployment. Our results highlight the importance of the bargaining structure for the assessment of a particular UI scheme. Most importantly, it depends on the relative size of the unions whether efficiency favors a uniform or a differentiated UI scheme.
Labour‐market Institutions and Macroeconomic Shocks
Authors: Chen Yu‐Fu , Snower Dennis , Zoega Gylfi
Published: August 2003

Abstract.  Macroeconomic shocks and labour‐market institutions jointly determine employment growth and economic performance. The effect of shocks depends on the nature of these institutions and the effect of institutional change depends on the macroeconomic environment. It follows that a given set of institutions may be appropriate in one epoch and not in another. We derive a dynamic model of labour demand in which the effect of firing costs on labour demand depends on the macroeconomic environment: when the level of macroeconomic activity is expected to drop and/or the trend rate of productivity growth is small, a rise in firing costs affects mainly (and adversely) the hiring decision and not the layoff decision. This makes firing costs harmful to employment when it may appear most appropriate. In contrast, firing costs can raise employment during periods of high growth and positive shocks. Our hypothesis is supported by empirical results using OECD data.
The Unemployed Individual's Marginal Willingness to Pay for the Remaining Entitlement Period
Authors: Van Ommeren Jos
Published: August 2003

Abstract.  This paper introduces a method of estimating the unemployed individual's marginal willingness to pay for the remaining entitlement period by application of search theory. It is demonstrated that search theory implies that the unemployed individual's marginal willingness to pay for the remaining entitlement period must be less than the value of the unemployment benefit. When benefits expire, though, the willingness to pay for an additional period must be equal to the benefit received during that period. The empirical relevance of this method is shown by re‐interpreting the studies of Meyer (Econometrica 58: 757–782, 1990) and Katz and Meyer (Journal of Public Economics 41: 45–72, 1990).
Labor Market Effects of Population Aging
Authors: Börsch‐Supan Axel
Published: August 2003

Abstract. This paper analyses effects of population aging on the labor market and determines their broad implications for public policy. It takes Germany as an example, but it equally applies to the other large economies in Continental Europe. The paper argues that, alongside the amply discussed, demographically‐determined increase in the contribution and tax burden which is responsible for the ever widening gap between gross and disposable earnings, two other important areas of policy deserve greater attention. First, it is unlikely that the decline in the relative size of the economically active population will be offset by higher capital intensity. Labor productivity will need to increase over and above this mechanism in order to compensate for the impact of population aging on domestic production. Hence, we will need more education and training to speed up human capital formation. Second, the shift in the age structure will also change the structure of demand for goods. This, in turn, will have large effects on the pattern of employment across different sectors of the economy and will require a substantial increase in labor mobility in order to accommodate these structural changes.
Differential Mortality and the Design of the Italian System of Public Pensions
Authors: Caselli Graziella , Peracchi Franco , Barbi Elisabetta , Lipsi Rosa Maria
Published: August 2003

Abstract. This paper considers the issue of actuarial fairness of the new Italian public pension system in view of the recent trends in old‐age mortality and the survival differences by gender, birth cohort and region of residence. After reviewing the secular trends in elderly mortality in Italy, and the evolution of regional differences in survival over the last three decades, we evaluate the impact, on the conversion factors introduced by the Dini reform, of a further decline in elderly mortality over the next few decades. We compute the conversion factors using a close approximation to the unknown formula employed in the Dini reform but allowing for gender‐ and region‐specific survival probabilities. Our results leave no doubt about the importance of frequently updating the conversion factors in the light of the rapid increase in elderly survival. The paper also quantifies to what extent gender‐ and region‐specific conversion factors may differ from their currently legislated values, that only vary by age. Finally, we recognize that the actuarial fairness of the system introduced by the recent reform can only be guaranteed on average and that, in the presence of a heterogeneous population of individuals that differ considerably in their mortality prospects, the current system implies a substantial degree of redistribution from high‐mortality groups (typically characterized by low income and low wealth) to low‐mortality groups (typically characterized by high income and high wealth).
Social Security Wealth and Retirement Decisions in Italy
Authors: Brugiavini Agar , Peracchi Franco
Published: August 2003

Abstract.  This paper uses administrative data to study the retirement decisions of Italian private‐sector non‐agricultural employees during the period 1977–97. Our analysis tries to assess the importance of the financial incentives built into the social security system. The basic idea is very simple: at any given age, and based on the available information, workers compare the expected present value of two alternatives: retiring today or working one more year, and then choose the best one.

A key role in this kind of comparisons is played by social security wealth, whose level and changes reflect the expectations about the profile of future earnings and the institutional features of the social security system. The various incentive measures that we consider differ in the precise weight given to the social security wealth that workers accrue as they continue to work.

Our model does not provide a structural representation of the retirement process. A worker's decision is modeled here following a ‘quasi reduced‐form’ approach, with the incentive measures entering as predictors of the worker's choice in addition to standard variables. The estimated models are then used to predict retirement probabilities under alternative policies that change social security wealth and derived incentive measures.
A Simple Intertemporal Model of Retirement Estimated On Italian Cross‐Section Data
Authors: Colombino Ugo
Published: August 2003

Abstract.  We develop and estimate a simple structural intertemporal model of retirement, using cross‐section Italian data. Under certain assumptions, the condition for being in retirement or alternatively in employment status at a certain date reduces to a static comparison between the instantaneous utility as employed and the instantaneous utility as retired (minus the future opportunity cost of retiring) at that date. Forward‐looking versus myopic versions of the model are obtained by including or dropping the term measuring the future loss of retiring. The model can easily be formulated under two opposite hypotheses — no savings and no borrowing versus perfect credit market (perfect consumption smoothing). The implications of the estimates are illustrated by simulating the effects of changes in the parameters of the pension system or in the demographic variables. In particular, the elasticity of the number of individuals in retirement status with respect to the pension turns out to be small but not irrelevant from the perspective of the long‐term design and evaluation of the pension system.