bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential phosphorylation of band 3 and glycophorin in intact and extracted erythrocyte membranes
Authors: Hosey M. Marlene , Tao Mariano 
Published: May 2005

AbstractThis report presents an analysis of the phosphorylation of human and rabbit erythrocyte membrane proteins which migrate in NaDodSO4‐polyacrylamide gels in the area of the Coomassie Blue‐stained proteins generally known as band 3. The phosphorylation of these proteins is of interest as band 3 has been implicated in transport processes. This study shows that there are at least three distinct phosphoproteins associated with the band 3 region of human erythrocyte membranes. These are band 2.9, the major band 3, and PAS‐1. The phosphorylation of these proteins is differentially catalyzed by solubilized membrane and cytoplasmic cyclic AMP‐dependent and ‐independent erythrocyte protein kinases. Band 2.9 is present and phosphorylated in unfractionated human and rabbit erythrocyte ghosts but not in NaI‐ or dimethylmaleic anhydride (DMMA)‐extracted membranes. These latter membrane preparations are enriched in band 3 and in sialoglycoproteins. The NaI‐extracted ghosts contain residual protein kinase activity which can catalyze the autophosphorylation of band 3 whereas the DMMA‐extracted ghosts are usually devoid of any kinase activity. However, both NaI‐ and DMMA‐extracted ghosts, as well as Triton X‐100 extracts of the DMMA‐extracted ghosts, can be phosphorylated by various erythrocyte protein kinases. The kinases which preferentially phosphorylate the major band 3 protein are inactive towards PAS‐1 while the kinases active towards PAS‐1 are less active towards band 3. The band 3 protein in the DMMA‐extracted ghosts can be cross‐linked with the Cu2+ ‐σ‐phenanthroline complex. The cross‐linking of band 3 does not affect its capacity to serve as a phosphoryl acceptor nor does phosphorylation affect the capacity of band 3 to form cross‐links. In addition to band 2.9, the major band 3 and PAS‐1, another minor protein component appears to be present in the band 3 region in human erythrocyte membranes. This protein is specifically phosphorylated by the cyclic AMP‐dependent protein kinases isolated from the cytoplasm of rabbit erythrocytes. The rabbit erythrocyte membranes lack PAS‐1 and the cyclic AMP‐dependent protein kinase substrate.
Crystallographic and chemical studies of the L‐arabinose‐binding protein from E. coli
Authors: Quiocho F. A. , Gilliland G. L. , Miller D. M. , Newcomer M. E. 
Published: May 2005

AbstractThe crystal structure of the L‐arabinose‐binding protein (ABP), an essential component of the high affinity L‐arabinose transport system in E. coli, has been determined at 3.5‐ and 2.8‐Å resolutions. The Fourier maps indicate that the molecule is ellipsoidal with overall dimensions of 70 × 35 × 35 Å (axial ratio ≃ 2:1) and consists of 2 distinct globular domains (designated “P” and “Q”). A tentative trace of the polypeptide backbone is presented. The 2 domains are arranged to create a deep and narrow cleft, the base of which is which is formed by 3 polypeptide chain segments linking the 2 domains. The arrangements of the secondary structure of the 2 domains are remarkably similar and can be related by a pseudo‐twofold axis. Each domain has a pleated sheet core with 2 helices on either side of the plane of the β sheet. This secondary structural arrangement is similar to that found in other proteins, specifically the dehydrogenases and kinases. The structural similarity is particularly intriguing in light of the recent finding in this laboratory that the dye 2′,4′,5′,7′‐tetraiodofluorescein, an adenine analogue which has been shown to bind to several dehydrogenases and kinases, binds to ABP with a dissociation constant of 30 μM.Experiments performed with protein, modified with the chromophoric probe 2‐chloromercuri‐4‐nitrophenol (MNP), suggest that the binding site is near an essential cysteine residue: modification of the thiol with the mercurial dramatically decreases the ligand‐binding affinity of ABP, and conversely, the sugar protects the cysteine from reaction with MNP. The binding of L‐arabinose to MNP‐labeled protein perturbs the nitrophenol absorbance spectrum. The essential cysteine has been assigned to position 64 in the proposed chain tracing, which is consistent with the amino acid sequence. As an explanation for the failure of the difference Fourier analyses to locate the sugar‐binding site, it is postulated that the structure has been solved with the sugar bound. Electron density to which no amino acid residue can be assigned and which could be the sugar molecule is within van der Waals distance of the sulfur atom.
A role for anion transport in the regulation of release from chromaffin granules and exocytosis from cells
Authors: Pollard Harvey B. , Pazoles Christopher J. , Creutz Carl E. , Ramu Avner , Strott Charles A. , Ray Probhati , Brown Edward M. , Aurbach G. D. , Tack‐Goldman Karen M. , Shulman N. Raphael 
Published: May 2005

AbstractRelease of epinephrine from isolated adrenergic secretory veiscles from the adrenal medulla (chromaffin granules) was found to be inhibited by a number of anion transport blocking agents, including SITS, probenecid, pyridoxal phosphate, and Na‐isethionate. High concentrations of permeant anion, such as chloride, are required for granule release and the drugs were found to be competitive inhibitors with respect to chloride. The anion transport blockers were also found to suppress exocytosis of serotonin from human platelets and parathyroid hormone from dissociated bovine parathyroid cells. By contrast, they had no effect on ACTH‐activated corticosterone secretion from dissociated rate adrenocortical cells, a process which occurs by diffusion rather than exocytosis. The important anion in the medium for human platelets was hydroxyl ion, rather than chloride, and the most effective drug on platelets was suramin. Isethionate was inactive. In the case of PTH secretion, both chloride and hydroxyl ions were important anions and were both competitively inhibited by anion blocking drugs including Na‐isethionate. We conclude from these studies that the chemistry of exocytosis appears to be quite similar to the chemistry of release from isolated secretory vesicles. We suggest that when vesicles are fused to plasma membranes prior to exocytosis they are exposed to higher chloride and hydroxyl ion concentrations of the medium, and that inward anion flux into the vesicle promotes release, possibly by local osmotic lysis. Blockade of exocytosis by anion transport blocking drugs would occur by inhibition of inward anion flux into the fused vesicle, by analogy with previous results from studies on isolated chromaffin granules.
Surface antigens of the embryonic chick myoblast: Expression on freshly trypsinized cells
Authors: Friedlander Martin , Fischman Donald A. 
Published: May 2005

AbstractUsing an antiserum raised in rabbits against embryonic chick skeletal myoblasts (Anti‐M‐24), we have examined the trypsin and neuraminidase sensitivity and physiological expression of myogenic cell surface antigens. It was found that trypsin‐released muscle cells more effectively inhibited, on a cell to cell basis, the cytotoxicity of Anti‐M‐24 for 24‐h‐old myoblast monolayers than did identical cells that had received a 3–4 h suspension culture recovery period from trypsinization. There was no such difference in absorptive capacities observed for any other embryonic chick tissue tested (e.g. brain, retina, liver, heart, and red blood cells) when freshly trypsinized cells were compared to ones which were given a 3–4 h culture period. If freshly trypsinized muscle cells were treated with high concentrations (30,000 international units (IU)/0.1 ml packed cells) of trypsin or with neuraminidase (30,000 IU/ml packed cells), there was a selective loss of myoblast‐specific surface antigens. When single cells that had been in suspension culture for 3.5 h were reexposed to low concentrations (10,000 IU/0.1 ml packed cells) of trypsin, more antigenic sites were revealed on their surfaces as detected by an increased absorptive capacity in removing myoblast‐binding antibodies from Anti‐M‐24. This increase in antigenic expression was time‐dependent and inversely related to the length of culture time after trypsinization. Immunofluorescence studies revealed that tissue specific myoblast cell surface antigens are present on both muscle cells that were freshly dissociated and those that had been in suspension culture for 3–4 h. Furthermore, freshly trypsinized myoblasts possessed cell surface components that were highly antigenic; antiserum to such cells reacted extensively with both trypsinized and recovered muscle cells as detected by complement‐dependent 51Cr release cytotoxicity assays and immunofluorescence. We conclude that embryonic chick myoblasts prossess surface antigens that may be selectively removed by neuraminidase or high concentrations of trypsin. These antigens may be progressively masked, with increasing time of culture after protease‐dissociation, by molecules that are sensitive to low concentrations of trypsin. Such masking of tissue‐specific cell surface antigens could result in the display of molecular mosaics which may play a role in facilitating intercellular recognition and subsequent differentiation and histogenesis.
Energetics and molecular biology of active transport in bacterial membrane vesicles
Authors: Kaback H. R. , Ramos S. , Robertson D. E. , Stroobant P. , Tokuda H. 
Published: May 2005

AbstractBacterial membrane vesicles retain the same sidedness as the membrane in the intact cell and catalyze active transport of many solutes by a respiration‐dependent mechanism that does not involve the generation of utilization of ATP or other high‐energy phosphate compounds. In E. coli vesicles, most of these transport systems are coupled to an electrochemical gradient of protons (ΔμH +, interior negative and alkaline) generated primarily by the oxidation of D‐lactate or reduced phenazine methosulfate via a membrane‐bound respiratory chain. Oxygen or, under appropriate conditions, fumarate or nitrate can function as terminal electron acceptors, and the site at which ΔμH + is generated is located before cytochrome b1 in the respiratory chain.Certain (N‐dansyl)aminoalkyl‐β‐D‐galactopyranosides (Dns‐gal) and N(2‐nitro‐4‐azidophenyl)aminoalkyl 1‐thio‐β‐D‐galactopyranosides (APG) are competitive inhibitors of lactose transport but are not transported themselves. Various fluorescence techniques, direct binding assays, and photoinactivation studies demonstrate that the great bulk of the lac carrier protein (ca. 95%) does not bind ligand in the absence of energy‐coupling. Upon generation of a ΔμH + (interior negative and alkaline), binding of Dns‐gal and APG‐dependent photoinactivation are observed. The data indicate that energy is coupled to the initial step in the transport process, and suggest that the lac carrier protein may be negatively charged.
Sialic acid: A specific role in hematopoietic spleen colony formation
Authors: Tonelli Quentin , Meints Russel H. 
Published: May 2005

AbstractVibrio cholerae neuraminidase (VCN) treatment of donor bone marrow cells results in a reduction in the number of hematopoietic colonies (CFUs) formed in the spleens of lethally irradiated mice. Treatment of marrow cells with sodium periodate under mild conditions, known to preferentially oxidze sialic acid, also reduced CFUs while subsequent potassium borohydride reduction restored CFUs to 80% of control levels. Innoculum viability as measured by in vitro incorporation of tritiated precursors into proteins, nucleic acids, and oligosaccharides was unaffected by VCN treatment. The ability of bone marrow cells in culture to respond to the hormone erythropoietin, as measured by the incorporation of 59Fe into cyclohexanone‐extractable heme, was also not affected by neuraminidase, making a cytotoxic effect of the VCN preparation unlikely. Incubation of VCN‐treated marrow with either β‐galactosidase or trypsin had no effect on the VCN‐induced reduction in CFUs. These results are consistent with the idea that membrane sialic acid plays a direct and specific role in the implantation and development of CFUs.
Dimensions and specificities of recognition sites on lectins and antibodies
Authors: Kabat Elvin A. 
Published: May 2005

AbstractA comparison is made of the specific combining sites of a number of lectins and of antibodies with emphasis on those reacting with blood group A, B, and H determinants. The ranges of site sizes and specificities of both groups are similar both from immunochemical studies and from the limited x‐ray diffraction data available.
Influence of increased membrane cholesterol on membrane fluidity and cell function in human red blood cells
Authors: Cooper Richard A. 
Published: May 2005

AbstractCholesterol and phospholipid are the two major lipids of the red cell membrane. Cholesterol is insoluble in water but is solubilized by phospholipids both in membranes and in plasma lipoproteins. Morever, cholesterol exchanges between membranes and lipoproteins. An equilibrium partition is established based on the amount of cholesterol relative to phospholipid (C/PL) in these two compartments.Increases in the C/PL of red cell membranes have been studied under three conditions: First, spontaneous increases in vivo have been observed in the spur red cells of patients with severe liver disease; second, similar red cell changes in vivo have been induced by the administration of cholesterol‐enriched diets to rodents and dogs; third, increases in membrane cholesterol have been induced in vitro by enriching the C/PL of the lipoprotein environment with cholesterol‐phospholipid dispersions (liposomes) having a C/PL of >1.0. In each case, there is a close relationship between the C/PL of the plasma environment and the C/PL of the red cell membrane. In vivo, the C/PL mole ratio of red cell membranes ranges from a normal value of 0.9–1.0 to values which approach but do not reach 2.0. In vitro, this ratio approaches 3.0.Cholesterol enrichment of red cell membranes directly influences membrane lipid fluidity, as assessed by the rotational diffusion of hydrophobic fluorescent probes such as diphenyl hexatriene (DPH). A close correlation exists between increases in red cell membrane C/PL and decreases in membrane fluidity over the range of membrane C/PL from 1.0 to 2.0; however, little further change in fluidity occurs when membrane C/PL is increased to 2.0–3.0.Cholesterol enrichment of red cell membranes is associated with the transformation of cell contour to one which is redundant and folded, and this is associated with a decrease in red cell filterability in vitro. Circulation in vivo in the presence of the slpeen further modifies cell shape to a spiny, irregular (spur) form, and the survival of cholesterol‐rich red cells is decreased in the presence of the spleen. Although active Na‐K transport is not influenced by cholesterol enrichment of human red cells, several carrier‐mediated transport pathways are inhibited. We have demonstrated this effect for the cotransport of Na + K and similar results have been obtained by others in studies of organic acid transport and the transport of small neutral molecules such as erythritol and glycerol.Thus, red cell membrane C/PL is sensitive to the C/PL of the plasma environment. Increasing membrane C/PL causes a decrease in membrane fluidity, and these changes are associated with a reduction in membrane permeability, a distortion of cell contour and filterability and a shortening of the survival of redcells in vivo.
Characterization of the glucose transporter from human erythrocytes
Authors: Sogin David C. , Hinkle Peter C. 
Published: May 2005

AbstractThe D‐glucose transporter from human erythrocytes has been purified and reconstituted by Kasahara and Hinkle (J Biol Chem 252:7394–7390). Using a similar purification scheme, we have isolated the protein with 65% of the extracted phospholipid at a lipid‐protein ratio of 14:1 by weight. The KD (0.14 μM) and extent (11 nmoles/mg protein) for binding of 3H‐cytochalasin B was determined by equilibrium dialysis. Glucose was a linear competitive inhibitor of binding of cytochalasin B, with an inhibition constant of 30 mM. To further characterize the protein, samples were filtered in the presence of sodium dodecyl sulfate (SDS) through Sepharose 6B to remove 95% of the lipid followed by filtration of Sephadex G150 to remove the remaining lipid and a contaminating amount of a minor, lower‐molecular‐weight protein. This preparation contains only 24% acidic and basic amino acids. The protein also contains 5% neutral sugars (of which 3% is galactose), 7% glucosamine, and 5% sialic acid.
Regulation of the receptor‐mediated cyclic AMP response of kidney to parathyroid hormone in the vitamin D‐deficient rat
Authors: Forte Leonard R. , Carnes David L. , Nickols G. Allen , Anast Constantine S. 
Published: May 2005

AbstractRats fed a diet deficient in vitamin D were found to exhibit a refractory cyclic AMP response of kidney slices to parathyroid hormone and a marked decrease in membrane parathyroid hormone‐dependent adenylate cyclase activity. Both the characteristic calcium deficiency (hypocalcemia) and secondary elevation of circulating parathyroid hormone appeared before the first noticeable decrease in hormone‐dependent enzyme activity. After repletion of D‐deficient rats with vitamin D2, we found that serum calcium and parathyroid hormone were both restored to normal levels before the depressed enzyme response to the hormone was reversed. Moreover, infusion of parathyroid hormone into vitamin D‐replete rats led to a marked reduction in parathyroid hormone‐dependent adenylate cyclase activity, which was partly restored to control level 3 hours after discontinuing the hormone infusion. Taken as a whole, this study suggests that the elevated endogenous parathyroid hormone in the vitamin D‐deficient rat is involved in the “down‐regulation” of renal cyclic AMP responsiveness to the hormone. However, these experiments do not rule out the possibility that calcium deficiency and/or vitamin D per se participate in the regulation of the renal cyclic AMP response to parathyroid hormone.
The Escherichia coli adenylate cyclase complex: Activation by phosphoenolpyruvate
Authors: Peterkofsky Alan , Gazdar Celia 
Published: May 2005

AbstractA model for the regulation of the activity of Escherichia coli adenylate cyclase is presented. It is proposed that Enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) interacts in a regulatory sense with the catalytic unit of adenylate cyclase. The phosphoenolpyruvate (PEP)‐dependent phosphorylation of Enzyme I is assumed to be associated with a high activity state of adenylate cyclase. The pyruvate or sugar‐dependent dephosphorylation of Enzyme I is correlated with a low activity state of adenylate cyclase. Evidence in support of the proposed model involves the observation that Enzyme I mutants have low cAMP levels and that PEP increases cellular cAMP levels and, under certain conditions, activates adenylate cyclase, Kinetic studies indicate that various ligands have opposing effects on adenylate cyclase. While PEP activates the enzyme, either glucose or pyruvate inhibit it. The unique relationships of PEP and Enzyme I to adenylate cyclase activity are discussed.
Modulator binding protein antagonizes activation of (Ca2+ + Mg2+)‐ATPase and Ca2+ transport of red blood cell membranes
Authors: Larsen Fred L. , Raess Beat U. , Hinds Thomas R. , Vincenzi Frank F. 
Published: May 2005

AbstractRed blood cells contain a protein that activates membrane‐bound (Ca2+ + Mg2+)‐ATPase and Ca2+ transport. The red blood cell activator protein is similar to a modulator protein that stimulates cyclic AMP phosphodiesterase. Wang and Desai [Journal of Biological Chemistry 252:4175–4184, 1977] described a modulator‐binding protein that antagonizes the activation of cyclic AMP phosphodiesterase by modulator protein. In the present work, modulator‐binding protein was shown to antagonize the activation of (Ca2+ + Mg2+)‐ATPase and Ca2+ transport by red blood cell activator protein. The results further demonstrate the similarity between the activator protein from human red blood cells and the modulator protein from bovine brain.
Formation of γ‐glutamyl‐ϵ‐lysine bridges between membrane proteins by a Ca2+‐regulated enzyme in intact erythrocytes
Authors: Lorand L. , Siefring G. E. , Lowe‐Krentz L. 
Published: May 2005

AbstractA rise in the intracellular concentration of Ca2+‐ions in human erythrocytes causes the formation of high‐molecular‐weight membrane protein polymers, cross‐linked by γ‐glutamyl‐ϵ‐lysine side chain bridges. Cross‐linking involves proteins at the cytoplasmic side of the membrane (band 4.1, spectrin, and band 3 materials) and the reaction is catalyzed by the intrinsic transglutaminase. This enzyme is regulated by Ca2+‐ions and it exists in a latent form in normal cells. The protein polymer, isolated from the membranes of Ca2+‐loaded intact human red cells, is heterogeneous in size and may contain as many as 6 moles of γ‐glutamyl‐ϵ‐lysine cross‐links per 100,000 gm of protein.Synthetic compounds, which either compete against the ϵ‐lysine cross‐linking functionalities of the protein substrates (eg, histamine, aminoacetonitrile, cystamine) or directly inactivate the transamidase (eg, cystamine), inhibit the membrane polymerization reaction in intact human erythrocytes. They also interfere with the Ca2+‐induced irreversible shape change from discocyte to echinocyte and inhibit the irreversible loss of membrane deformability. Thus, the transamidase‐catalyzed production of γ‐glutamyl‐ϵ‐lysine cross‐links in the membrane may be a common denominator in these cellular manifestations.