bluuebunny/crossref_metadata_2025 huggingface dataset:
Multivariate analysis of
Drosophila
courtship
Authors: Markow Therese A. , Hanson Stephen J.
Published: May 2006

Courtship records of 15 pairs of
Drosophila melanogaster
were analyzed for temporal stationarity of courtship behaviors, behavioral diversity, behavioral intercorrelations, sequential properties, and information transmission for both sexes. Durations of one male behavior, “orient-back,” and two female behaviors, “preen” and “stand still,” were found to change from the first to the second half of courtship. Male diversity was greater than female diversity, and both were stationary over time. Correlation analyses failed to single out any particular male or female behaviors as being influential in controlling courtship duration. Male behavior sequences formed several multibehavior loops; female behavior consisted of only a few terminal two-tuple transitions. Transmission analysis carried out on the joint male/female transition matrix showed a higher transmission rate from males to females (12%) than from females to males (7%). Potential applications of this multivariate analysis to investigations of neurobiological and evolutionary aspects of
Drosophila
courtship behavior are proposed.
beta-Thalassemia present in cis to a new beta-chain structural variant, Hb Vicksburg [beta 75 (E19)Leu leads to 0].
Authors: Adams J G , Steinberg M H , Newman M V , Morrison W T , Benz E J , Iyer R
Published: May 2006

Hemoglobin Vicksburg was discovered in a 6-year-old Black boy who had been anemic since infancy. Examination of his hemolysate revealed 87.5% Hb F, 2.4% Hb A2, and 7.6% Hb Vicksburg, which had the electrophoretic and chromatographic properties of Hb A. Structural analysis of Hb Vicksburg demonstrated a deletion of leucine at beta 75(E19), a new variant. Hb Vicksburg was neither unstable nor subject to posttranslational degradation. The alpha/non-alpha biosynthetic ratio was 2.6. Because the proband appeared to be a mixed heterozygote for Hb Vicksburg and beta 0-thalassemia, Hb Vicksburg should have comprised the major portion of the hemolysate. Thus, Hb Vicksburg was synthesized at a rate considerably lower than would be expected on the basis of gene dosage. There was no reason to suspect abnormal translation of beta Vicksburg mRNA; in individuals with Hb St. Antoine (beta 74 and beta 75 deleted), the abnormal hemoglobin comprised 25% of the hemolysate in the simple heterozygote yet was unstable. Deletion of beta 75, therefore, would not in itself appear to lead to diminished synthesis. There was a profound deficit of beta Vicksburg mRNA when measured by liquid hybridization analysis with beta cDNA. The most plausible explanation for the low output of Hb Vicksburg is that a mutation for beta +-thalassemia is present in cis to the structural mutation.
Quantitative analysis of melanoma-associated antigen p97 in normal and neoplastic tissues.
Authors: Brown J P , Woodbury R G , Hart C E , Hellström I , Hellström K E
Published: May 2006

We have used two highly sensitive assays to quantitate p97, a protein associated with human melanoma, in cultured cells and normal adult, fetal, and neoplastic tissues. To measure p97 at the surface of intact cells, radiolabeled Fab fragments of a monoclonal antibody specific for p97 were used in a binding assay. To measure p97 in detergent-solubilized membrane preparations, we used a novel double-determinant immunoassay that uses two monoclonal antibodies to two distinct antigenic determinants of p97. These assays revealed that although p97 is present in small amounts in normal adult tissues, it is present in much larger amounts in most melanomas, in some other tumors (both benign and malignant), and in certain fetal tissues. We conclude that monoclonal antibodies to p97 may prove to be of value for the diagnosis and therapy of melanoma.
Vertical transmission of susceptibility to stuttering with sex-modified expression.
Authors: Kidd K K , Heimbuch R C , Records M A
Published: May 2006

Stuttering is not usually considered genetic, although it has long been known to be familial. Data collected on 2035 relatives of 397 unrelated adult stutterers confirm and quantify the strong familial concentration. Our analytic approach to these family data, one that does not require specification of a genetic hypothesis, shows that stuttering among relatives occurs in a pattern indicating vertical transmission of a susceptibility to stuttering with sex-modified expression. Although simple Mendelian hypotheses are not sufficient to explain the observed pattern of stuttering in families, more complex genetic models can explain the pattern. In the past, such evidence has been considered sufficient, because it does not preclude the possibility of cultural transmission. However, certain cultural transmission hypotheses previously proposed for stuttering are excluded by these data. The findings in this study support a growing opinion among speech pathologists that most stuttering is a genetically inherited neurologic disorder.
Cultured muscle from myotonic muscular dystrophy patients: altered membrane electrical properties.
Authors: Merickel M , Gray R , Chauvin P , Appel S
Published: May 2006

Myotonic muscular dystrophy (MyD) is an inherited human disease involving skeletal muscle as well as many other organ systems. We have approached the study of this disorder by growing normal and diseased human muscle in a primary tissue culture system and investigating some of the electrical properties of the resulting myotubes. The most distinctive abnormality noted in MyD myotubes was an increased tendency to fire repetitive action potentials. A decreased action potential afterhyperpolarization amplitude and the presence of depolarizing afterpotentials were also noted, as were a decreased resting membrane potential, decreased action potential amplitude and overshoot, and decreased outward-going rectification. Although the ionic basis of these abnormal properties in vitro is not clearly defined, changes in the slow outward-going potassium current offer the best explanation. Furthermore, MyD cell culture offers a valuable model for critical analysis of the molecular mechanisms underlying MyD deficits.
Directionality and polarity in recA protein-promoted branch migration.
Authors: Cox M M , Lehman I R
Published: May 2006

The recA protein of Escherichia coli promotes the complete exchange of strands between full-length linear duplex and single-stranded circular phi X174 DNA molecules. Analysis of the reaction by electron microscopy confirms that D loops containing short heteroduplex regions are rapidly formed at the ends of the linear duplex, followed by a relatively slow branch migration that converts the D loops to nicked circular duplexes (RFII) and displaced linear single strands. Heteroduplex extension and displacement of the linear single strand are concerted. Heterologous sequences within the linear duplex halt branch migration and lead to the accumulation of D loops. Although D loops can be formed at either end of the linear duplex, recA protein-promoted branch migration proceeds uniquely in the 3' leads to 5' direction relative to the (--) strand of the linear duplex.
Structured habitats and the evolution of anticompetitor toxins in bacteria.
Authors: Chao L , Levin B R
Published: May 2006

We demonstrate that in liquid cultures, defined in this study as a mass habitat, the outcome of competition between Escherichia coli that produce an antibacterial toxin (colicin) and sensitive E. coli is frequency dependent; the colicinogenic bacteria are at an advantage only when fairly common (frequencies in excess of 2 X 10(-2)). However, we also show that in a soft agar matrix, a structured habitat, the colicinogenic bacteria have an advantage even when initially rare (frequencies as low as 10(-6)). These contrasting outcomes are attributed to the colicinogenic bacteria's lower intrinsic growth rate relative to the sensitive bacteria and the different manner in which bacteria and resources are partitioned in the two types of habitats. Bacteria in a liquid culture exist as randomly distributed individuals and the killing of sensitive bacteria by the colicin augments the amount of resource available to the colicinogenic bacteria to an extent identical to that experienced by the surviving sensitive bacteria. On the other hand, the bacteria in a soft agar matrix exist as single-clone colonies. As the colicinogenic colonies release colicin, they kill neighboring sensitive bacteria and form an inhibition zone around themselves. By this action, they increase the concentration of resources around themselves and overcome their growth rate disadvantage. We suggest that structured habitats are more favorable for the evolution of colicinogenic bacteria.
Metal thiolate clusters in cobalt(II)-metallothionein.
Authors: Vasák M , Kägi J H
Published: May 2006

Rabbit liver metallothionein-1 in which all seven metal-binding sites are occupied by cobalt(II) exhibits spectral features typical of tetrathiolate coordination with approximate Td microsymmetry [Vasák, M. (1980) J. Am. Chem. Soc. 102, 3953-3955]. With a total of 20 cysteine residues per molecule, this mode of metal binding implies that some of the thiolate ligands are shared by neighboring Co(II) ions, resulting in clustered structures. In this study, evidence for the existence of thiolate-linked Co(II) clusters is presented and their mode of formation is explored by comparing the optical and magnetic properties of forms of Co(II)-metallothionein containing 1-7 equivalents of Co(II). Preparations with up to 4 Co(II) equivalents display electronic spectra in the d-d and charge-transfer regions that resemble those of isolated tetrahedral Co(II)-tetrathiolate complexes. Upon binding of more than four Co(II) ions, however, the spectrum changes progressively and approaches in the fully saturated Co(II)-metallothionein an absorption profile similar to that of crystallographically defined model (Co)II-tetrathiolate clusters [Dance, I. G. (1979) J. Am. Chem. Soc. 101, 6264-6273]. These effects are closely paralleled by changes in the ESR spectrum. Above 4 Co(II) equivalents per thionein, the ESR signal at gx approximately 5.9 measured at 4 K decreases progressively in intensity, until in the fully occupied protein the complex is nearly diamagnetic. These changes, which were confirmed by measurements of paramagnetic susceptibility, establish the existence of Co(II) thiolate clusters in Co(II)-metallothionein. The loss of paramagnetism reflects most likely antiferromagnetic coupling of neighboring Co(II) ions brought about by a superexchange mechanism via the thiolate bridging ligands.
Mitochondrial regulation of phosphocreatine/inorganic phosphate ratios in exercising human muscle: a gated 31P NMR study.
Authors: Chance B , Eleff S , Leigh J S , Sokolow D , Sapega A
Published: May 2006

31P NMR is used to determine the relationship between work output in the exercising human forearm and the steady-state capability of oxidative phosphorylation as measured by the phosphocreatine/inorganic phosphate ratio (PCr/Pi). Exercise intensities (one contraction per 5 sec) permitting comfortable continuation of activity for greater than 1 hr produced PCr/Pi of about 1 for a subject of moderate training. Linear relationships between work rate per unit volume of muscle and the 5-min mean PCr/Pi were found for the subject's left and right arms. The protocol affords sensitive criteria of muscle performance in normal subjects and of biochemical or vascular disease in abnormal subjects. The Pi, PCr, and ATP levels found by 31P NMR represent the initial values in the cycle of contraction and relaxation which permit restitution of resting state 4 prior to the next contraction and the continuation of steady-state work performance.
The bacteriorhodopsin gene.
Authors: Dunn R , McCoy J , Simsek M , Majumdar A , Chang S H , Rajbhandary U L , Khorana H G
Published: May 2006

The bacteriorhodopsin gene has been identified in a 5.3-kilobase restriction endonuclease fragment isolated from Halobacterium halobium DNA, using a cloned cDNA fragment as the probe. Of the 1229 nucleotides whose sequence was determined in the genomic fragment, 786 correspond to the structural gene of bacteriorhodopsin, 360 are upstream from the initiator methionine codon, and 83 are downstream from the COOH terminus. The bacteriorhodopsin gene codes for a precursor sequence of 13 amino acids at the NH2 terminus, 248 amino acids that are present in the mature protein and an additional aspartic acid at the COOH terminus. This determination of the DNA sequence for an archaebacterial gene reveals that the standard genetic code is used; however, there is a marked preference for either G or C in the third codon position. The gene does not contain any intervening sequences and no prokaryotic promoter can be identified in the region immediately upstream from the structural gene. The bacteriorhodopsin mRNA contains at the 5' terminus only three nucleotides beyond the initiating AUG codon and this terminus can form a hairpin structure. Immediately downstream from this structure there is a sequence complementary to the 3' terminus of H. halobium 16S rRNA.
Possible occurrence and role of an essential histidyl residue in succinate dehydrogenase.
Authors: Vik S B , Hatefi Y
Published: May 2006

Diethylpyrocarbonate (Et2PC) inhibits the succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1] activity of submitochondrial particles, Complex II (succinate:ubiquinone oxidoreductase), and the soluble, pure succinate dehydrogenase. The reaction order with respect to Et2PC concentration is close to unity, suggesting modification of one essential residue per active unit of the enzyme. The pH profile of Et2PC inhibition, the partial reversal of inhibition by hydroxylamine, and the spectral change of the Et2PC-treated enzyme in the UV region suggest modification of a histidyl residue. Succinate dehydrogenase activity can be protected against Et2PC inhibition by succinate, fumarate, malonate, or oxaloacetate (also by activating anions such as ClO4(-) and Br-), suggesting that the Et2PC-modified essential residue might be at the active site. In both submitochondrial particles and the purified enzyme, succinate dehydrogenase activity is highest and relatively constant at pH greater than or equal to 7.0 and diminishes precipitously at pH less than 7.0. By contrast, fumarate reductase activity is highest at pH less than or equal to 7.0 and diminishes at pH greater than 7.0. These results are consistent with the possible participation of the unprotonated and protonated forms of the imidazole moiety of the putative histidyl residue, respectively, in succinate oxidation and fumarate reduction.
Hemin inhibits ATP-dependent ubiquitin-dependent proteolysis: role of hemin in regulating ubiquitin conjugate degradation.
Authors: Haas A L , Rose I A
Published: May 2006

Hemin has been shown to inhibit specifically the energy-dependent degradation of normal and abnormal proteins in reticulocytes [Etlinger, J. D. & Goldberg, A. L. (1980) J. Biol. Chem. 255, 4563-4568]. The present work demonstrates that the action of hemin involves the multi-enzyme ATP-dependent ubiquitin-dependent proteolytic system exclusively. At a concentration of approximately 25 microM, hemin produces 50% inhibition of the degradation of 125I-labeled bovine serum albumin by this pathway. Hemin has no effect on the basal rate of proteolysis in the absence of either ATP or ubiquitin. At a concentration of hemin that gives complete inhibition of proteolysis, ATP-dependent formation of ubiquitin conjugates continues at about 50% of the control rate but the degradation of these ubiquitin conjugates is completely blocked. Inhibition of overall proteolysis and conjugate degradation are sensitive to hemin concentration to exactly the same extent. Hemin inhibition of conjugate breakdown results in the accumulation of higher molecular weight conjugates that are lost when hemin is removed by dilution. A model is proposed in which hemin acts as a negative allosteric effector in the initial step of a sequential degradative path by which intact ubiquitin conjugates are first cleaved to ubiquitin-associated fragments.
Microtubules and microfilaments during cell spreading and colony formation in PK 15 epithelial cells.
Authors: Connolly J A , Kalnins V I , Barber B H
Published: May 2006

We have studied the distribution of microtubules and microfilaments during the cell spreading and subsequent colony formation in PK 15 pig kidney epithelial cells using indirect immunofluorescence. During the cell spreading on a solid substratum, microtubules grew out from the region around the nucleus, and a collar of microfilament bundles formed around the cell periphery. Although virtually all well-spread cells showed a complex microtubular network, distinctly different patterns of stress fibers were observed. In small colonies, the most commonly observed pattern was a ring of microfilament bundles that appeared to be in register between adjacent cells and encircled the entire colony in a fashion similar to that seen in single cells. In large colonies (more than 50 cells), approximately 60% of the cells displayed clearly stained microfilament bundles, either at the cell periphery or throughout their cytoplasm, whereas in the remaining 40%, no microfilament bundles were observed and only the outline of the cells was delineated by interaction with anti-actin. Such "negative" cells were seen in groups alongside "positive" cells (i.e., cells possessing extensive stress fiber networks) within the same colony. Independent of their stress fiber phenotype, all cells maintained a flattened shape and an extensive network of microtubules. We suggest that dense microfilament bundles are not a uniform feature of well-spread PI 15 cells in culture and that a loss of microfilament bundle occurs in some cells.
Quantitation and characterization of a species-specific and embryo stage-dependent 55-kilodalton phosphoprotein also present in cells transformed by simian virus 40.
Authors: Chandrasekaran K , McFarland V W , Simmons D T , Dziadek M , Gurney E G , Mora P T
Published: May 2006

A 55-kilodalton (kDal) protein was detected recently in primary cultures of day 12 mouse embryos by immunoprecipitation with serum from simian virus 40 (SV40) tumor-bearing hamsters (T serum), Preliminary evidence suggested that this protein was similar to a cellular 55-kDal protein induced after SV40 transformation of mouse cells. We now show that specific approximately 55-kDal [35S]methionine-labeled proteins precipitate from primary cultures of midgestation mouse, rat, and hamster embryos on addition of T serum or monoclonal antiserum prepared against the SV40-induced mouse 55-kDal proteins. The two-dimensional maps of the [35S]methionine-labeled tryptic peptides of the mouse, hamster, and rat embryo proteins are similar to the maps of the corresponding proteins from SV40-transformed cells. Primary cells from midgestation mouse, hamster, or rat embryos contain one-third to one-half as much 55-kDal protein as a SV40-transformed mouse fibroblast cell and nearly the same amount as F9 mouse embryonal carcinoma cells. The amount of 55-kDal protein is greatly reduced on replating the mouse, rat, or hamster embryo primary cells. The amount of this protein in mouse embryos is dependent on the stage of the embryo. The embryo proteins are phosphoproteins.
Site-specific inversion sequence of the herpes simplex virus genome: Domain and structural features
Authors: Mocarski Edward S. , Roizman Bernard
Published: May 2006

The genome of herpes simplex virus-1 consists of two covalently linked components, L and S, that invert relative to each other. The L and S components consist of unique DNA sequences bracketed by inverted repeats. The inverted repeats of the L component are designated
ab
and
b
′
a
′ and those of the S component are designated
a
′
c
′ and
ca
. The number of
a
sequences at the termini and at the L-S component junction varies from one to several copies. Insertion into the middle of the L component of a DNA fragment consisting of 156 base pairs (bp) of the
b
sequence, an entire
a
sequence of 501 bp, and 618 bp of the
c
sequence created a new site through which additional inversions in the genome occurred. Comparison of the nucleotide sequences of DNA fragments containing one and two
a
sequences defined the domain of the
a
sequence. The single
a
sequence consists of two 20-bp direct repeats (designated as DR1) bracketing a region that contains 19 tandem direct repeats of a 12-bp sequence (DR2) adjacent to three direct repeats of a 37-bp sequence (DR4), in addition to short stretches of unique sequences. The fragment with two tandem
a
sequences contained three copies of DR1—i.e., the intervening DR1 was shared by the two
a
sequences. Furthermore, one
a
sequence contained 22 copies of DR2 and two copies of DR4 whereas the second
a
sequence contained 19 copies of DR2 and two copies of DR4. These observations suggest that (
i
) amplification of the number of terminal and internal
a
sequences is the consequence of intramolecular or intermolecular recombination through DR1, (
ii
) the number of copies of DR2 and DR4 within the
a
sequence is not fixed and may vary as a consequence of unequal crossing over or slippage, and (
iii
) inversion results from intramolecular recombination between terminal and inverted
a
sequences.
RETRACTED: Recovery from prolonged abnormalities of canine myocardium salvaged from ischemic necrosis by coronary reperfusion.
Authors: Kloner R A , DeBoer L W , Darsee J R , Ingwall J S , Braunwald E
Published: May 2006

The purpose of this study was to determine whether or not the biochemical, functional, and ultrastructural abnormalities produced by brief temporary coronary occlusions (unassociated with necrosis) ever resolve and, if so, when they do. Anesthetized open-chest dogs were subjected to 15 min of coronary artery occlusion followed by 72 hr, 7 days, or 14 days of reperfusion. Serial in vivo myocardial biopsies were performed for measurement of ATP and for ultrastructural analysis. Regional function was evaluated by sonomicrometry. Mean (+/- SEM) myocardial ATP concentration was 36.6 +/- 1.2 nmol/mg of cardiac protein in nonischemic subendocardium and 18.9 +/- 1.5 in ischemic subendocardium after 15 min of ischemia. ATP remainede performed for measurement of ATP and for ultrastructural analysis. Regional function was evaluated by sonomicrometry. Mean (+/- SEM) myocardial ATP concentration was 36.6 +/- 1.2 nmol/mg of cardiac protein in nonischemic subendocardium and 18.9 +/- 1.5 in ischemic subendocardium after 15 min of ischemia. ATP remainede performed for measurement of ATP and for ultrastructural analysis. Regional function was evaluated by sonomicrometry. Mean (+/- SEM) myocardial ATP concentration was 36.6 +/- 1.2 nmol/mg of cardiac protein in nonischemic subendocardium and 18.9 +/- 1.5 in ischemic subendocardium after 15 min of ischemia. ATP remained depressed in the reperfused previously ischemic subendocardium at both 90 min (68% of nonischemic value) and 72 hr (78% of nonischemic value) but returned to normal at 7 days. Regional systolic function and cardiac ultrastructural abnormalities required 7 days for full recovery. Histologic and histochemical analysis did not reveal necrosis at any time. Therefore, biochemical, functional, and ultrastructural abnormalities induced by brief periods of transient coronary occlusion not associated with necrosis do resolve completely but the recovery period is prolonged.
Kinetic parameters for acetylcholine interaction in intact neuromuscular junction.
Authors: Land B R , Salpeter E E , Salpeter M M
Published: May 2006

The dependency of miniature endplate current (mepc) rise time upon mepc amplitude and acetylcholine receptor site density was measured in lizard intercostal muscles and used to fit the rate constants in a simple kinetic scheme. The kinetic scheme included diffusion, two-step sequential binding of acetylcholine to receptor, and opening of the ion channel. Numerical simulation of the observed mepc behavior yielded the following kinetic constants; (i) diffusion constant, 4 X 10(-6) cm2 sec-1; (ii) forward binding rates, 4.7 X 10(7) M-1 sec-1; (iii) channel relaxation rate, 25 msec-1. The value above for the forward binding rates assumed both rates to be equal. If they are different, the slower of the two is in the range of 2-5 X 10(7) M-1 sec-1. A radial profile of bound receptor indicated that activation of the receptor was very local, occurring essentially within a radius of about 0.3 micrometers from the point of acetylcholine release.
Molecular structure of a double helix that has non-Watson—Crick type base pairing formed by 2-substituted poly(A) and poly(U)
Authors: Hakoshima Toshio , Fukui Toshikazu , Ikehara Morio , Tomita Ken-ichi
Published: May 2006

X-ray fiber diffraction studies of duplexes formed by 2-substituted poly(A) and poly(U) provide evidence for the existence of a double helical structure of poly(A)·poly(U) held together by Hoogsteen-type base pairing with parallel chain polarity.
Swainsonine: an inhibitor of glycoprotein processing.
Authors: Elbein A D , Solf R , Dorling P R , Vosbeck K
Published: May 2006

Swainsonine, an indolizidine alkaloid, inhibits the processing of asparagine-linked glycoproteins in both cell-free extracts and animal cells in culture. Thus, in a liver particulate enzyme preparation, swainsonine at 0.1-1.0 microM inhibited the mannosidase that releases [3H]mannose from a high mannose glycopeptide but only slightly inhibited the release of glucose from a glucose-labeled glycopeptide. MDCK and Chinese hamster ovary cells in culture incorporate [2-3H]mannose and [6-3H]glucosamine into both high mannose and complex types of oligosaccharides. When these cells were incubated with swainsonine and then labeled with mannose or glucosamine, there was a dramatic decrease in the amount of label in the complex type of glycopeptide and a substantial increase in the radioactivity in the high mannose type. This change was monitored by the increase in radioactivity that became susceptible to digestion by endoglucosaminidase H with increasing concentrations of swainosine. The endoglucosaminidase H-released oligosaccharide(s) from swainsonine-treated cells was larger and more homogeneous than that from controls and eluted from Bio-Gel P-4 at the position of Man9GlcNAc. Several tissue culture cell lines were grown in the presence of swainsonine to determine its effect on cell surface glycoproteins. Cells grown in the alkaloid showed an increased capacity to bind Escherichia coli B886, a bacterium that binds to high mannose glycoproteins. These cells also showed an increasing binding of [3H]concanavalin A.
Erythrocyte ankyrin: immunoreactive analogues are associated with mitotic structures in cultured cells and with microtubules in brain.
Authors: Bennett V , Davis J
Published: May 2006

Human erythrocyte ankyrin, the membrane attachment protein for spectrin, has been detected by radioimmunoassay in a variety of cells and tissues. This report identifies polypeptides crossreacting with ankyrin in brain and HeLa cells and demonstrates that one function of these ankyrin analogues involves association with microtubules. Ankyrin immunoreactivity was localized by indirect immunofluorescence in a colchicine- and detergent-sensitive cytoplasmic meshwork in interphase cells. There also was specific nuclear staining, localized in a bright spots, which was displaced entirely by ankyrin or by high molecular weight microtubule-associated proteins (MAPs) from brain. In dividing cells, the punctate nuclear staining and the meshwork disappeared. Fluorescence was localized at the spindle pole during metaphase and was redistributed to the cleavage furrow in later stages of mitosis. An immunoreactive Mr 370,000 polypeptide comigrating with MAP1 was identified in brain extracts and copolymerized with microtubules through repeated cycles of polymerization and depolymerization. Finally, erythrocyte ankyrin associated with microtubules prepared from pure tubulin, and this binding was displaced by brain MAPs.
Rat liver gap junction protein: properties and partial sequence.
Authors: Nicholson B J , Hunkapiller M W , Grim L B , Hood L E , Revel J P
Published: May 2006

Gap junctions, strongly implicated as channels for direct cell-to-cell communication, have been isolated from rat liver in high yield and purity. These gap junction fractions contain few morphologically recognizable contaminants, but NaDodSO4/polyacrylamide gel electrophoresis reveals a number of polypeptides. With the exception of a nonjunctional component of Mr 38,000 and some poorly soluble material, including collagen, all the polypeptides have very similar or identical two-dimensional peptide maps and arise from proteolytic cleavage of the COOH-terminus or aggregation of a Mr 28,000 protein. We report the sequence of the NH2-terminal 52 amino acids of this protein. The polypeptide (Mr approximately equal to 10,000) characteristic of trypsin-treated gap junction preparations is shown to be two distinct polypeptides, both derived from the Mr 28,000 protein.
A cellular protein that associates with the transforming protein of Rous sarcoma virus is also a heat-shock protein.
Authors: Oppermann H , Levinson W , Bishop J M
Published: May 2006

A single viral protein (pp60src) mediates neoplastic transformation of cells infected with Rous sarcoma virus. Immunoprecipitation of pp60src has revealed two cellular proteins (Mr 50,000 and 89,000) that appear to associate with pp60src in a specific manner. Neither of the cellular proteins has been well characterized, but it is thought that both may participate in the function of pp60src. Treatment of avian cells with unphysiological temperature or certain chemical agents amplifies the production of several proteins in the manner of the "heat shock" response earlier described for Drosophila. We report here that one of these proteins, with a molecular weight of 89,000 is identical to the 89-kilodalton protein found associated with pp60src. The 89-kilodalton protein is a major constituent of both uninfected and infected cells, even in the absence of inducing agents, but only a small fraction of this protein appears to associate with pp60src in cells transformed by Rous sarcoma virus. The complex containing pp60src and the 89-kilodalton protein can be precipitated by an immune reaction involving pp60src alone. The complexed form of the 89-kilodalton protein did not react directly with antibodies but regained its reactivity subsequent to release from the complex. We conclude that the 89-kilodalton protein is bound to pp60src in a relatively stable complex. We suggest that the 89-kilodalton protein may have overlapping roles in viral oncogenesis and the heat shock response, and that evidence on the function of the protein in either setting may illuminate its function in the other. In addition, it may prove profitable to search for other overlaps between the cellular response to heat shock and the neoplastic transformation of cells by pp60src.
Symmetry breaking and pattern selection in far-from-equilibrium systems
Authors: Nicolis G. , Prigogine I.
Published: May 2006

A mechanism enabling nonequilibrium systems to select spatially asymmetric solutions is outlined. It operates when a macroscopic mode undergoing a symmetry-breaking bifurcation can interact with a polar or a chiral field not explicitly involved in the bifurcation. The perturbation of the bifurcation induced by the field allows the system to capture the external asymmetry and build patterns of preferred polarity or preferred chirality. The chemical and biological implications of forming such an asymmetric medium are discussed.
Mechanism of araC autoregulation and the domains of two overlapping promoters, Pc and PBAD, in the L-arabinose regulatory region of Escherichia coli.
Authors: Lee N L , Gielow W O , Wallace R G
Published: May 2006

The DNA-protein contact sites in the ara regulatory region, which contains the promoters for araBAD and araC, have been determined for araC protein, the cyclic AMP-binding protein, and RNA polymerase, by using the methylation protection and DNase I protection methods. The functional significance of binding was assessed by correlating the state of occupancy of these sites with promoter activity in transcription initiation. Our results suggest that the basis for araC autoregulation is that araC protein, in either its activator (P2) or repressor (P1) form, acts as a repressor for araC, by binding to the RNA polymerase attachment site at the araC promoter. We also found that the araC and araBAD promoters share a common site of positive control by the cyclic AMP-binding protein, located 90 bases from the araBAD and 60 bases from the araC transcriptional start points. A model for the mechanism of regulation of araBAD and araC expression by the catabolite gene-activator protein, P1, and Pe is proposed. An earlier model proposed by Ogden et al. [Ogden S., Haggerty, D., Stoner, C. M., Kolodrubetz, D. & Schleif, R. (1980) Proc. Natl. Acad. Sci, USA 77, 3346-3350] is discussed in the light of the data presented in this paper.
Two small RNAs encoded by Epstein-Barr virus and complexed with protein are precipitated by antibodies from patients with systemic lupus erythematosus.
Authors: Lerner M R , Andrews N C , Miller G , Steitz J A
Published: May 2006

Primate cells harboring the Epstein-Barr virus (EBV) genome synthesize large amounts of two small RNAs:EBER 1 and EBER 2 (EBV-encoded RNA). These RNAs are approximately 180 nucleotides long, possess 5' pppA termini, and lack poly(A). They have different T1 and pancreatic RNase digestion fingerprints. They are not found in normal B lymphocytes, in transformed B lymphocytes that lack EBV DNA, in T lymphocytes transformed by Herpesvirus ateles, or in a variety of other nonlymphoid mammalian cells. Hybridization analyses indicate that EBER 1 and EBER 2 are encoded by the EcoRI-J fragment of EBV (B95-8) DNA. In vivo both RNAs are associated with protein(s), allowing their specific precipitation by the systemic lupus erythematosus-associated antibody anti-La. The La antigen in uninfected mammalian cells consists of a heterogeneous class of small ribonucleoprotein particles, some of whose RNA components exhibit sequence homology with a highly repetitive, interspersed class of human DNA designated the Alu family. Possible functions for EBER 1 and EBER 2 in infection and cell transformation by EBV and their potential relationship to the pathogenesis of systemic lupus erythematosus are discussed.
Multiple functional domains of the heparin molecule.
Authors: Oosta G M , Gardner W T , Beeler D L , Rosenberg R D
Published: May 2006

Affinity-fractionated porcine heparin was randomly scissioned by chemical techniques to give hexasaccharides, octasaccharides, decasaccharides, and mucopolysaccharide fragments of approximately 14 residues and approximately 16 residues that were able to complex with the protease inhibitor. Direct measurements of the kinetic behavior of the hexasaccharides, octasaccharides, and decasaccharides showed that these fractions greatly enhanced the rate of Factor Xa inactivation by antithrombin. Indeed, these species exhibited specific molar activities that ranged from 6.9% (hexaccharide) to 60.9% (decasaccharide) of that of the heparin fragment of approximately 16 residues. However, these oligosaccharides exhibited essentially no ability to accelerate thrombin-antithrombin interactions. The avidity of the hexasaccharides, octasaccharides, and decasaccharides for the protease inhibitor increased as a function of size with the respective dissociation constants ranging from 5.5 X 10(-6) M to 2.9 X 10(-7) M. These data suggest that the region of the heparin molecule needed for catalyzing Factor Xa-antithrombin interaction is intimately related to the antithrombin binding domain. The smallest complex carbohydrate fragment that accelerated the inactivation of thrombin by antithrombin had approximately 14 residues. This fraction had an avidity for the protease inhibitor of 2.8 X 10(-7) M and specific molar activities of 140 units per mumol (thrombin neutralization) and 460 units per mumol (factor Xa inactivation). The largest heparin fragment examined contained approximately 16 residues. This fraction had an avidity for antithrombin of 2.4 X 10(-7) M and specific molar activities of 500 units per mumol (thrombin neutralization) and 560 units per mumol (Factor Xa inactivation). Detailed kinetic analyses showed that these two species are able to directly activate antithrombin to the same extent with respect to thrombin inhibition. However, the larger mucopolysaccharide fragment is also capable of approximating free enzyme with protease inhibitor.
Human lymphoblasts contain DNA glycosylase activity excising N-3 and N-7 methyl and ethyl purines but not O6-alkylguanines or 1-alkyladenines.
Authors: Singer B , Brent T P
Published: May 2006

Cultured human lymphoblasts (CCRF-CEM line) have DNA glycosylase activities, the specificities of which were investigated by using high-performance liquid chromatography. In addition to 3-methyladenine, 3-ethyladenine, 7-methylguanine, 7-ethylguanine, 3-methylguanine, and 3-ethylguanine also were excised from alkylated double-stranded DNA and deoxypolynucleotides, but 1-methyladenine, 1-ethyladenine, O6-methylguanine, and O6-ethylguanine were not. The glycosylase activity was generally greater for the methylated than for the corresponding ethylated purines and was also greater toward 3-alkyladenine than toward 3-alkyladenine than toward 3-alkylguanine. 7-Methylguanine and 7-ethylguanine were excised to similar but low extents. However, in molar terms, the release of 7-methylguanine was similar to that of 3-methyladenine.
Voltage-dependent inactivation of a calcium channel.
Authors: Fox A P
Published: May 2006

The inactivation of Ca currents in unfertilized eggs of the marine polychaete Neanthes arenaceodentata was investigated by using a voltage clamp technique. These Ca currents do not appear to be masked by other currents in the voltage range studied. Inactivation increased monotonically with increasing depolarization and occurred at potentials more negative than the inward Ca current. Currents elicited by depolarization at different Ca concentrations had approximately the same time course of inactivation, even though the size of the currents varied by almost an order of magnitude. There was complete inactivation in solutions containing Ca, Sr, or Ba (all permeant) for depolarizations beyond -30 mV absolute; the time course of the inactivation process was similar for all three permeant ions. Increasing depolarizations toward the expected equilibrium potential for Ca, Ba, or Sr did not produce any lessening of the inactivation. Thus, it appears that the inactivation seen in Neanthes eggs is a purely voltage-dependent phenomenon.
Energies and kinetics of radical pairs involving bacteriochlorophyll and bacteriopheophytin in bacterial reaction centers
Authors: Shuvalov Vladimir A. , Parson William W.
Published: May 2006

Absorbance changes reflecting the formation of a transient radical-pair state, P
F
, were measured in reaction centers from
Rhodopseudomonas sphaeroides
under conditions that blocked electron transfer to a later carrier (a quinone, Q). The temperature dependence of the absorbance changes suggests that P
F
is an equilibrium mixture of two states, which appear to be mainly
1
[P
[unk]
B
[unk]
] and
1
[P
[unk]
H
[unk]
]. P is a bacteriochlorophyll dimer, B is a bacteriochlorophyll absorbing at 800 nm, and H is a bacteriopheophytin. In the presence of Q
[unk]
, the energy of
1
[P
[unk]
B
[unk]
] is about 0.025 eV above that of
1
[P
[unk]
H
[unk]
],
1
[P
[unk]
H
[unk]
] can decay to a triplet state, P
R
, which also is an equilibrium mixture of two states, separated by about 0.03 eV. The lower of these appears to be mainly a locally excited triplet state of P,
3
P; the upper state contains a major contribution from a triplet charge-transfer state,
3
[P
[unk]
B
[unk]
]. The temperature dependence of delayed fluorescence from P
R
indicates that
3
P lies 0.40 eV below the excited singlet state, P
*
, which is about 0.05 eV above
1
[P
[unk]
H
[unk]
]. The
1,3
[P
[unk]
B
[unk]
] charge-transfer states thus appear to interact with the locally excited states of P and B to give singlet and triplet states that are separated in energy by about 0.35 eV. This is 10
6
times larger than the splitting between
1
[P
[unk]
H
[unk]
] and
3
[P
[unk]
H
[unk]
] and implies strong orbital overlap between P
[unk]
and B
[unk]
. This is consistent with recent picosecond studies which suggest that electron transfer from P
*
to B occurs within 1 ps and is followed in 4 to 10 ps by electron transfer from B
[unk]
to H.
Continuous fluorescence microphotolysis: A sensitive method for study of diffusion processes in single cells
Authors: Peters Reiner , Brünger Axel , Schulten Klaus
Published: May 2006

Continuous fluorescence microphotolysis is a sensitive method for the study of translational diffusion in the plasma membrane of single living cells and related systems. In this communication the conceptual basis of the method and its theoretical framework and experimental realization, as well as applications, are reported. In continuous fluorescence microphotolysis a microscopic membrane area of a single fluorescently labeled cell is irradiated by a laser beam while the fluorescence emitted from the area is monitored. The decay of the measuring signal reflects the competition of two processes: (
i
) the elimination of fluorophores by irreversible photolysis, and (
ii
) the entrance of new fluorophores into the area by diffusion. Rate constants for the two processes can be derived from the measuring data by mathematical analysis. As compared to our initial approach, fluorescence microphotolysis [Peters, R., Peters, J., Tews, K. H. & Bähr, W. (1974)
Biochim. Biophys. Acta
367, 282-294], the main advantage of the method described here is an improvement of data quality and detection limit by orders of magnitude. From the practical point of view the main advantage is a simplification of the experimental setup. Results obtained by this method are encouraging and support the contention that continuous fluorescence microphotolysis may disclose new aspects of diffusion processes in biological systems.
Photoaffinity labeling of an herbicide receptor protein in chloroplast membranes
Authors: Pfister Klaus , Steinback Katherine E. , Gardner Gary , Arntzen Charles J.
Published: May 2006

2-Azido-4-ethylamino-6-isopropylamino-
s
-triazine (azido-atrazine) inhibits photosynthetic electron transport at a site identical to that affected by atrazine (2-chloro-4-ethylamino-6-isopropylamino-
s
-triazine). The latter is a well-characterized inhibitor of photosystem II reactions. Azido-atrazine was used as a photoaffinity label to identify the herbicide receptor protein; UV irradiation of chloroplast thylakoids in the presence of azido[
14
C]atrazine resulted in the covalent attachment of radioactive inhibitor to thylakoid membranes isolated from pea seedlings and from a triazine-susceptible biotype of the weed
Amaranthus hybridus
. No covalent binding of azido-atrazine was observed for thylakoid membranes isolated from a naturally occurring triazine-resistant biotype of
A. hybridus
. Analysis of thylakoid polypeptides from both the susceptible and resistant
A. hybridus
biotypes by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, followed by fluorography to locate
14
C label, demonstrated specific association of the azido[
14
C]atrazine with polypeptides of the 34- to 32-kilodalton size class in susceptible but not in resistant membranes.
Regulation of intracellular levels of calmodulin and tubulin in normal and transformed cells.
Authors: Chafouleas J G , Pardue R L , Brinkley B R , Dedman J R , Means A R
Published: May 2006

Transformation of mammalian tissue culture cells by oncogenic viruses results in a 2-fold increase in the intracellular concentration of calmodulin quantitated by radioimmunoassay. The two pairs of companion cell lines used in this study were the Swiss mouse 3T3/simian virus 40-transformed 3T3 cells and the normal rat kidney (NRK)/Rous sarcoma virus-transformed NRK cells. The increased intracellular levels of calmodulin in the transformed cells are due to a greater increase in the rate of synthesis (3-fold) relative to the change in the rate of degradation (1.4-fold). On the other hand, no increases were observed in tubulin levels as quantitated by a colchicine-binding assay. The lack of change in tubulin concentration was accounted for by a 2-fold increase in the rate of degradation that is compensated by a similar increase in the rate of synthesis. The consequence of such changes in both transformed cell types is a 2-fold increase in the calmodulin-to-tubulin protein ratio relative to that in their nontransformed counterparts.
DNA sequences preceding the rabbit beta-globin gene are required for formation in mouse L cells of beta-globin RNA with the correct 5' terminus.
Authors: Dierks P , van Ooyen A , Mantei N , Weissmann C
Published: May 2006

Mouse thymidine kinase-negative (TK-) L cells were transformed with concatenates of cloned herpes simplex virus 1 TK DNA and different rabbit beta-globin DNAs in which the globin genes were preceded by native flanking sequences of 14, 66, 76, 425, and 1500 nucleotides.l In all cases, selection for TK+ cell lines led to a high yield of lines producing 5-1500 mature rabbit beta-globin-specific RNA strands per cell. The 5' termini of the transcripts mapped to (i) the "cap" nucleotide, (ii) positions 42 to 48 nucleotides downstream from the cap site, or (iii) positions in the vector DNA preceding the gene. In the case of the gene with only 14 base pairs of 5' flanking sequence, a high level of rabbit beta-globin RNA was produced, but none of the transcripts had the correct 5' end; most of them originated in the vector moiety. With 66 base pairs of 5' flanking sequence, 5% of the 5' termini were correct, and with 76 or more base pairs, 30-85% were correct. The region between 14 and 66 base pairs preceding the cap site contains the Hogness box and appears to be essential for correct initiation of transcription. The region between 66 and 76 base pairs before the cap site contains a variant of the canonical sequence G-G-C-T-C-A-A-T-C-T found preceding many other genes at a similar location, and this region may modulate the efficiency of transcription. The sequence of 425 nucleotides preceding the rabbit beta-globin gene is reported.