bluuebunny/crossref_metadata_2025_split huggingface dataset:
The salt‐extractable fraction of dynein from sea urchin sperm flagella: An analysis by gel electrophoresis and by adenosine triphosphatase activity
Authors: Kincaid Jr. Harvey L. , Gibbons Barbara H. , Gibbons I. R. 
Published: May 2005

AbstractPrevious work has shown that the dynein from axonemes of sea urchin sperm consists of two distinct fractions which differ substantially in their extractability by salt. Upon gel electrophoresis of whole demembranated axonemes solubilized with sodium dodecyl sulfate, the dynein fraction shows two closely spaced bands with apparent molecular weights of 520,000 and 460,000; the proteins in these bands are termed the A and B components of the dynein. Similar electrophoresis of the soluble fraction obtained by extracting the axonemes with 0.5 M NaCl shows a single prominent band containing approximately half of the A component of the dynein (A1 component). The residue of extracted axonemes contain the other half of the A component of the dynein (A2 component) and all the B component. Densitometry of the bands indicates that the A1, A2 and B components of the dynein are present in approximately equal molar quantity. Electron microscopic studies show that the A1 component of the dynein constitutes the outer arms on the doublet tubules. Assay of ATPase activity in 0.05 M KCl and l mM ATP indicates about 65% of the total ATPase activity becomes soluble when the A1 component of the dynein is extracted with salt.
Three‐dimensional structures at 5.5 Å resolution and regulatory processes in aspartate transcarbamylase from E. coli
Authors: Lipscomb W. N. , Evans D. R. , Edwards B. F. P. , Warren S. G. , Pastra‐Landis S. , Wiley D. C. 
Published: May 2005

AbstractThe three‐dimensional structure of the multisubunit allosteric enzyme, aspartate transcarbamylase, has been determined to 5.5 Å resolution. An unusual feature of the molecule is a large central aqueous cavity 50 Å × 50 Å × 25 Å, into which the active sites face. Access to the central cavity and the active site region is provided by six equivalent channels of 15 Å diameter.A complex C6R4, composed of catalytic trimers C3 and of regulatory dimers R2, has been isolated upon treatment of aspartate transcarbamylase (ATCase, C6R6) by mercurials. The specific catalytic activity of C6R4 is essentially the same as that of ATCase, about 70% of that of the catalytic trimers at 30 mM aspartate and saturating carbamyl phosphate. Allosteric interactions are reduced in C6R4 as compared with those in ATCase. In the homotropic interactions the Hill coefficient is reduced from approximately 3.3 to 2.1 at pH 8.3, while the heterotropic interactions of both cytidine triphosphate (CTP) and adenosine triphosphate (ATP) are reduced substantially but not abolished at pH 8.3. Thus, the allosteric transitions involved in the regulatory mechanisms do not require the intact structure C6R6. Also, this regulation is not simply the control of access of substrates or products to or from the large central aqueous cavity in the ATCase molecule.Comparison of electron density maps at 5.5 Å resolution for ATCase and for the complex of ATCase with CTP shows substantial similarities throughout the three‐dimensional electron density maps. Significant differences are seen, however, in the region of the regulatory dimers R2 where CTP adds, and near the active sites in the catalytic trimers C3.
A regulator protein for the length determination of bacteriophage lambda tail
Authors: Katsura Isao , Kühl Peter W. 
Published: May 2005

AbstractMutants in gene U of phage λ produce polytails. Those polytails have a tail fiber and a basal part like normal tails, but their major tubular part is longer than that of normal tails and shows a wide length distribution.We established the morphogenetic pathway of the λ tail and found that U gene product (pU) acts throughout the assembly of the major tail protein (pV). Polytails in U− lysate are activated by pU in vitro and form long‐tailed phage which are infectious to a small extent.If the formation of the basal part of the tail is blocked, pV (the major tail protein) remains unassembled as long as pU is present in the cell. However, we found that part of pV assembles into giant polytubes of several microns in length in lysates of a double mutant U− · H− in which both the basal part and pU are absent.pV in purified tails can be dissociated into disks (about 10S) or smaller units (about 2.5S) in vitro under extreme conditions. The disks form polytubes efficiently under physiological conditions, but the smaller units do not form polytubes efficiently. The smaller units have in vitro complementation activity with V− lysate. In vitro complementation activities with V−, U−, and Z− lysates are detected in the dialyzed extracts of SDS gel electrophoresis of purified tails. The molecular weights of the polypeptide chains containing those activities are estimated to be 31,000, 14,000 and 20,000 daltons, respectively.
The transformation of τ particles into t4 heads. II. Transformations of the surface lattice an related observations on form determination
Authors: Aebi U. , Bijlenga R. , v. d. Broek J. , v. d. Broek R. , Eiserling F. , Kellenberger C. , Kellenberger E. , Mesyanzhinov V. , Müller L. , Showe M. , Smith R. , Steven A. 
Published: May 2005

AbstractIn part I of this paper (1) we give evidence that the P23‐capsoid of τ‐particles is transformed in situ into the P23*‐capsid of normal phage. Using the polymorphism of phage T4, we have chosen polyheads as representative of P23 assemblies and giant phages as representative of P23* assemblies in order to study their surface crystals by optical filtration of micrographs. We found for polyheads a lattice constant of 112 Å with the typical hexameric, ringlike capsomer and for the giants a lattice constant of 124 Å with quite a different capsomer morphology, of the type (6+1). From the stoichiometry of the proteins composing the normal capsid we conclude that the protomer is a single P23* molecule and that the minor capsid‐proteins must be in singular positions on the surface lattice or on the polyhedral head (center of capsomers, vertices, or basal part).We extrapolate the findings on the giant head to the normal head and give a geometric model which is consistent with 1,100 molecules of P23* per capsid.We discuss the part of form inheritance contributed by P23 and the other formgiving gene products and give evidence that morphologic characters are the result of pairs of a reaction chain of interacting gene products. The example we give is the giant head produced by a ts mutant in gene 24 at 36°C.
The mechanism of microtubule assembly in vitro
Authors: Kirschner Marc W. , Williams Robley C. 
Published: May 2005

AbstractThe mechanism of microtubule polymerization and depolymerization has been studied with protein purified from extracts of porcine brain. Under polymerizing conditions characteristic microtubules composed of parallel protofilaments are observed in the electron microscope. Under depolymerizing conditions three forms are observed: double rings of outside diameter 49 nm, spirals, and 7‐nm globular subunits. Under the same conditions two boundaries are observed in the analytical ultracentrifuge at 6S and 36S, whether depolymerization is accomplished by cooling to 0°C, by addition of 1 mM CaCl2 at 25°C, or by removal of GTP. On polymerization all of the 36S and most of the 6S is converted to a fast‐sedimenting form which the electron microscope reveals to be microtubules.The depolymerization mixture may be fractionated by gel chromatography into two fractions, one consisting solely of 6S and the other mostly 36S. Neither fraction regenerates the original equilibrium mixture. The 36S form may be reversibly dissociated into 6S subunits by addition of NaCl. From these and other considerations we have postulated that microtubule protein is composed of two different types of tubulin, both of which participate in polymerization. Studies are reported showing that colchicine does not dissociate microtubule rings but blocks polymerization by interfering with their proper lateral association into a protofilament array within microtubules. The role of GTP in polymerization is also discussed. Electron micrographic evidence is presented suggesting the conversion of protofilaments directly into rings and spirals, and a pathway for microtubule assembly is proposed.
Undelivered summary remarks for the 1974 squaw valley meeting on assembly mechanisms
Authors: Wood W. B. 
Published: May 2005

AbstractThe status of research on macromolecular assembly is similar in several respects to that of research on macromolecular synthesis in the late 1950's. The work of that era can teach us some lessons, but it also has left us with some preconceptions that may be misleading us in our attempts to understand assembly mechanisms.
The biochemistry of an acetylcholine receptor
Authors: Raftery M. A. , Vandlen R. , Michaelson D. , Bode J. , Moody T. , Chao Y. , Reed K. , Deutsch J. , Duguid J. 
Published: May 2005

AbstractThe acetylcholine receptor from Torpedo californica electroplax has been studied at three levels of molecular organization: receptor‐rich membrane fragments, solubilized and purified receptor, and reconstituted receptor in phospholipid vesicles. The binding of cholinergic ligands to the membrane‐bound and the solubilized material is not cooperative, and the number of ligand sites is less than the number of toxin sites. In addition, the purified macromolecule contains the molecular features necessary for ion‐translocation during postsynaptic depolarization, since a chemically excitable membrane can be formed from purified receptor and Torpedo phospholipids.
Reconstitution of mycoplasma membranes
Authors: Razin Shmuel 
Published: May 2005

AbstractDetergent‐solubilized proteins and lipids of mycoplasma membranes reassemble spontaneously into membranous structures on the removal or dilution of the detergent in the presence of divalent cations. The cations seem to function by neutralizing the negatively charged groups on membrane lipids and proteins which interfere by electrostatic repulsion with membrane reassembly. Moreover, salt bridges formed by the divalent cation between acidic groups on membrane proteins and lipids seem to play an important role in the reconstituted membrane stability. Electron transport activity, as measured by the transport of electrons from NADH to oxygen, has been demonstrated in reconstituted Acholeplasma laidlawii membranes. However, restoration of active transport of sugars or ions has not been achieved so far. The conditions for obtaining properly sealed vesicles, which are obligatory for demonstrating transport activity, are still rather poorly defined. The reassembled membranous structures cannot be distinguished from the native membranes in chemical composition, density, and thin sections. However, probe techniques, x‐ray diffraction, and freeze‐fracturing electron microscopy indicate that the proteins are organized differently in the reassembled membranes, though the lipid bilayer is restored. The results obtained so far leave little hope for successfully reconstituting the molecular organization of membranes as complex as those of mycoplasmas by a single‐step reassembly of detergent‐solubilized membrane components. The prospects appear brighter with membranes having only a few protein species, such as the outer membrane of gram‐negative bacteria. In spite of the failure to reconstitute fully active mycoplasma membranes, the reassembly procedure was found valuable in studying the interactions of detergent‐solubilized membrane proteins with lipids, the effects of a hydrophobic environment on hydrophilic enzymes, and the production of “hybrid” membranes having selected membrane components.
Biochemical characterization of the golgi complex of mammalian cells
Authors: Fleischer Becca , Zambrano Fernando , Fleischer Sidney 
Published: May 2005

AbstractWe have developed methods for the isolation of Golgi apparatus from a number of mammalian tissues. The Golgi is distinct both chemically and enzymatically from the other membranes of the cell. For both liver and kidney, galactosyltransferase has been found to be a useful marker enzyme for Golgi membranes. This enzyme is involved in the modification of glycoproteins during secretion. In addition to lipoproteins and glycoproteins, the Golgi apparatus of liver is involved in the secretion of albumin, a simple protein. It does not, however, take part in the synthesis of sphingomyelin, lecithin, or triglycerides which are present in the secreted lipoproteins. These lipids appear to be synthesized predominantly by the endoplasmic reticulum. In kidney, which is rich in glycolipids, 3′‐phosphoadenosine 5′‐phosphosulfate, an enzyme which converts cerebroside to sulfatide, is localized predominantly in the Golgi apparatus. Thus, Golgi functions to modify glycolipids as well as mucopolysaccharides and proteins. Sulfatide constitutes a significant fraction of the total lipid of both Golgi and plasma membranes of kidney. When 35S‐sulfate is injected into rats, it is incorporated first into the sulfatides of the Golgi apparatus and later appears in the sulfatides of the plasma membrane. The data are consistent with the view that sulfatides are formed in the Golgi apparatus of kidney and then transported to the plasma membrane.
Bacteriorhodopsin: Photosignal transduction and photoenergy transduction in different biological systems
Authors: Bogomolni Roberto A. , Stoeckenius Walther 
Published: May 2005

AbstractLiving organisms use light as a source of energy and as a source of information. They have developed highly specialized photoenergy and photosignal transducing devices which serve these functions. Membranes are essential parts of both photosignal and photoenergy transducing systems.In photoenergy transduction a substantial part of the absorbed energy is conserved for times very long compared to the lifetime of excited states and converted finally to chemical free energy of ATP and other forms in which it can be stored for further use by the organism. In photosignal transduction light typically triggers an event which dissipates much more energy than is absorbed in the form of light. The additional energy had been stored previously by the organism through some energy transducing systems.
Radioiodination of the envelope proteins of newcastle disease virus
Authors: Li Joseph K.‐K. , Fox C. Fred 
Published: May 2005

AbstractLactoperoxidase‐catalyzed iodination selectively labels the two glycoproteins (VP1 and VP2) of Newcastle disease virus. The low‐molecular‐weight, nonglycosylated major viral protein, VP6, was not iodinated in the intact virus but was iodinated in disrupted virions, suggesting a localization on the inner, rather than the outer envelope surface. Studies on the distribution of virion proteins labeled with 125I and 3H‐isoleucine between detergent‐soluble and detergent‐insoluble fractions show that the virion proteins VP4, VP5, and VP6 are solubilized to a much lesser extent than are VP1 and VP2.
The bound nucleotide of actin
Authors: Cooke Roger 
Published: May 2005

AbstractThe extent of actin polymerization has been studied for samples in which the bound nucleotide of the actin was ATP, ADP, or an analog of ATP that was not split (AMPPNP). The equilibrium constants for the addition of a monomer to a polymer end were determined from the concentration of monomer coexisting with the polymer. An analysis of these results concludes that the bound ATP on G‐actin provides little energy to promote the polymerization of the actin. AMPPNP was incorporated into F‐actin and the interaction of F‐actin · AMPPNP with myosin was studied. F‐actin · AMPPNP activated the ATPase of myosin to the same extent as did F‐actin · ADP. However, the rate of superprecipitation was slower in the case of F‐actin · AMPPNP than in the control.
The binding of Mn2+ and ADP to myosin
Authors: Martonosi Anthony 
Published: May 2005

AbstractThe metal ion requirement of myosin‐ADP binding was investigated by use of Mn2+. Mn2+ binds to two sets of noninteracting sites on myosin which are characterized by affinity constants of 106 and 103, M−1 at 0.016 M KCl concentration. The maximum number of sites is 2 for the high affinity and 20–25 for the low affinity set. Binding of Mn2+ to the high affinity sites increases the affinity of ADP binding to myosin.F‐actin inhibits ADP binding (Kiely, B., and Martonosi, A., Biochim. Biophys. Acta 172: 158–170 [1969]), but even at F‐actin concentrations much higher than that required to saturate the actin binding sites of myosin or its proteolytic fragments, significant ADP binding remained. The actin insensitive portion of ADP binding was inhibited by 10−4 M inorganic pyrophosphate or ATP. The results are discussed on the basis of a model in which actin and ADP bind to myosin at distinct but interacting sites.
Studies on the primary structure of 14 proteins from the large subunit of escherichia coli ribosomes with an improved protein sequenator and with mass spectrometry
Authors: Wittmann‐Liebold B. , Geissler A. W. , Marzinzig E. 
Published: May 2005

AbstractFourteen proteins from the large subunit of Escherichia coli ribosomes were analyzed in an improved sequenator. In addition to our previously described modifications of a Beckman sequenator, new valves which work free of a dead volume were constructed. By this and the previous improvements (e.g., a new vacuum system with a recorder, cool traps, automatic conversion) much better results were obtained than before. It was even possible to use (in addition to the standard methods, e.g., thin‐layer chromatography and amino acid analysis) mass spectrometry without preceding gas chromatography for identification of the released PTH amino acids. Our experience with the various methods, especially mass spectrometry, is described and the techniques are compared. The results obtained by the described methods on the amino acid sequences of the 14 ribosomal proteins are summarized.
Investigations of the possible role of proteases in altering surface proteins of virally transformed hamster fibroblasts
Authors: Hynes Richard O. , Pearlstein Edward S. 
Published: May 2005

AbstractVirally transformed fibroblasts have on their surfaces zero or reduced amounts of a large external transformation‐sensitive (LETS) glycoprotein. This protein is extremely sensitive to proteolysis. When prelabeled normal fibroblasts are cocultivated with transformed cells, the LETS glycoprotein of the normal cells shows an increased rate of turnover. Experiments are described which investigate the possibility that this phenomenon and the absence of LETS glycoprotein are due to proteolysis by the transformed cells. In particular, the role of plasminogen activation is examined by the use of protease inhibitors and plasminogen‐depleted serum. It is concluded that activation of plasminogen is not required for the disappearance of the LETS glycoprotein although the involvement of other proteases cannot be ruled out. The role of proteases in affecting cell growth and behavior is discussed.
Binding to specific receptors on oocyte plasma membranes by serum phosvitin‐lipovitellin
Authors: Yusko S. C. , Roth Thomas F. 
Published: May 2005

AbstractSpecific binding sites for the serum complex of phosvitin and lipovitellin have been shown to exist on the outer surface of rapidly growing chicken oocytes. The existence and specificity of these sites were demonstrated by competition for binding to unfixed oocyte membrane fragments and by displacement of already bound and labeled phosvitin‐lipovitellin from formaldehyde‐fixed membranes. Only unlabeled phosvitin‐lipovitellin competed with the 125I‐labeled complex for binding to the fragments or displacement of bound label; IgG isolated from egg yolks and bovine serum albumin were ineffective.
The cytochemical localization of adenylate cyclase activity in mucous and serous cells of the salivary gland
Authors: Kim Sun‐Kee 
Published: May 2005

AbstractThe present study was undertaken to localize adenylate cyclase activity in salivary glands by cytochemical means. For the study, serous parotid glands and mixed sublingual glands of the rat were used. Pieces of the fixed glands were incubated with adenosine triphosphate (ATP) or adenylyl‐imidodi‐phosphate (AMP‐PNP) as substrate: inorganic pyrophosphate or PNP liberated upon the action of adenylate cyclase on the substrates is precipitated by lead ions at their sites of production.In both glands, the reaction product was detected along the myoepithelial cell membranes in contact with secretory cells, indicating that a high level of adenylate cyclase activity occurs in association with these cell membranes. The association with a high level of the enzyme activity might be related to the contractile nature of myoepithelial cells which are supposed to aid secretory cells in discharging secretion products.A high level of adenylate cyclase activity was also detected associated with serous secretory cells (acinar cells of the parotid gland and demilune cells of the sublingual gland), but not with mucous secretory cells. In serous cells, deposits of reaction product were localized along the extracellular space of the apical cell membrane bordering the lumen. This is the portion of the cell membrane which fuses with the granule membranes during secretion. Since the granule membranes are not associated with a detectable level of adenylate cyclase activity, it appears that the enzyme activity becomes activated or associated with the granule membranes as they become part of the cell membrane by fusion. The association with a high level of adenylate cyclase activity appears to be related to the ability of the membrane to fuse with other membranes. It is likely, since the luminal membrane of mucous cells which does not fuse with mucous granule membranes during secretion is not associated with a detectable enzyme activity.
The HLB dependency for detergent solubilization of hormonally sensitive adenylate cyclase
Authors: Storm D. R. , Field S. O. , Ryan J. 
Published: May 2005

AbstractThe HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane‐enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary systematically with the length of the ethylene oxide chain for a homologous series of detergents such as the Triton X series. These detergents have a constant hydrophobic moiety, octylphenyl, and a variable polar portion, polyethoxyethanol. Basal‐NaF‐epine‐phrine‐, and glucagon‐stimulated adenylate cyclase activities were solubilized in the HLB range of 16.8–17.4. Solubilization was most effective in 0.01 M Tris buffers at pH 7.5 containing 1–5 mM mercaptoethanol, 1 mM MgCl2, and 0.1% Triton X‐305. The detergent to membrane protein ratio used in these studies was 3:1.Criteria for solubilization included lack of sedimentation at 100,000 × g, the absence of particulate material in the supernatant when examined by electron microscopy, and inclusion of hormonally sensitive adenylate cylcase activity in Sephadex G‐200 gels. The apparent molecular weight of the solubilized enzyme was approximately 200,000 in the presence of Triton X‐305. The solubilized enzyme was stimulated 5‐fold by NaF, 7‐fold by glucagon, and 20‐fold by epinephrine compared to the particulate enzyme used in this study which was stimulated 10‐fold, 3,4‐fold, and 4‐fold by NaF, epinephrine, and glucagon, respectively. The solubilized enzyme is stable for several weeks when stored at −60° C.