bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and partial characterization of the heterophile antigen of infectious mononucleosis from bovine erythrocytes
Authors: Merrick J. M. , Schifferle R. , Zadarlik K. , Kano K. , Milgrom F. 
Published: May 2005

AbstractThe heterophile antigen (Paul‐Bunnell antigen, PBA) of infectious mononucleosis was isolated by extraction of an aqueous suspension of bovine erythrocyte stromata with chloroform‐methanol (2:1). The upper aqueous layer contained gangliosides, PBA, and a high‐molecular‐weight glycoprotein. PBA and gangliosides were separated from the high‐molecular‐weight glycoprotein by extraction of lyophilized upper layer with chloroform‐methanol solvents. Separation of PBA from gangliosides was carried out by chromatography on DEAE‐cellulose with chloroform‐methanol solvents. PBA appeared to be a minor glycoprotein component of the erythrocyte membrane and had both hydrophobic and hydrophilic properties. It was soluble in either organic or aqueous solvents. On SDS‐polyacrylamide gel electrophoresis, it migrated as a single component that stained for protein with Coomassie blue, for carbohydrate with periodic acid‐Schiff reagent, and for lipid with oil red 0; it had an apparent molecular weight of 26,000. It was composed of 62% protein with major amino acids: glutamic acid, proline, glycine, isoleucine, leucine, and threonine (158, 116, 98, 90, 85, and 82 residues per 1,000 residues, respectively). Carbohydrate content was 9.2% with major sugar constituents: sialic acid, galactosamine, and galactose. Serologic activity of PBA was destroyed by pronase but not by trypsin.
Studies related to the head‐maturation pathway of bacteriophages T4 and T2: II. Nuclear disruption, protein synthesis and particle formation with the mutant 43−·30−·46−
Authors: Wunderli H. , Couture E. , Vince D. A. , Kellenberger E. 
Published: May 2005

AbstractWe describe the aberrant phage multiplication of the triple conditional lethal mutant 43−(polymerase)· 30−(ligase)·46−(exonuclease) of bacteriophage T4D in which phage DNA replication is arrested but some late protein synthesis occurs (33). The nuclear disruption is indistinguishable from wild type. Forty‐five empty small and empty large particles are assembled per cell when the multiplicity of infection (m.o.i.) is 100. This number corresponds closely to the 38 phage equivalents of cleaved major head protein determined biochemically. By reducing the m.o.i. the number of observable particles decreases, reaching 1–5 per cell at an m.o.i. of 5(+5).The total synthesis of phage related proteins is not significantly dependant on the m.o.i. The synthesis of late proteins is about 10% of that of wild type at high m.o.i. and decreases with the m.o.i. The different early and late proteins do not show the same relative proportions as in wild type and respond differently to an increased m.o.i. These and other results are discussed with respect to the role of phage DNA in prehead assembly and head maturation.
Plant lectins detect age and region specific differences in cell surface carbohydrates and cell reassociation behavior of embryonic mouse cerebellar cells
Authors: Hatten Mary E. , Sidman Richard L. 
Published: May 2005

AbstractWhen plated at high cell density in a microwell culture system, freshly dissociated embryonic mouse cerebellar cells assemble into reproducible, 3‐dimensional patterns. The addition of the dimeric lectin Succinyl Concanavalin A blocks reversibly the formation of the microwell pattern, suggesting that cell surface carbohydrates affect the reassociation behavior of embryonic mouse cerebellar cells.Agglutination studes of dissociated cell populations harvested from different regions of the embryonic brain reveal that different lectins agglutinate cell populations from different embryonic brain regions. Cells from E13 cerebellum are agglutinated with Concanavalin A, wheat germ agglutinin, Ricinus communis agglutinin, mol wt 60,000, Ricinus communis agglutinin, mol wt 120,000, and Lens culinaris, but not by soybean agglutinin or a fucose‐binding protein. Cells from the midbrain are agglutinated only with Concanavalin A, Ricinus communis agglutinin, mol wt 60,000 and Ricinus communis agglutinin, mol wt 120,000; those from the cerebral cortex are agglutinated only with Lens culinaris; and those from the medulla are agglutinated only with Ricinus communis agglutinin, mol wt 60,000, and Ricinus communis agglutinin, mol wt 120,000. In addition, agglutination of cerebellar cells with Concanavalin A, wheat germ agglutinin, and Ricinus communis agglutinin is diminished over the course of development from embryonic day 13 to postnatal day 7. These studies suggest regional differences in the cell surfaces of the developling brain that are further modulated during the differentiation of the tissues.On a poly(D‐lysine) treated substrate in microwell cultures, cell migration is unique to the cerebellum of the 4 brain regions studied. Surfaces treated with carbohydrate‐derivatized poly(D‐lysine) are currently being tested for their efficacy as substrates for differential cell migration.
Membrane assembly: Synthesis and intracellular processing of the vesicular stomatitis viral glycoprotein
Authors: Katz Flora N. , Rothman James E. , Knipe David M. , Lodish Harvey F. 
Published: May 2005

AbstractThe glycoprotein (G) of vesicular stomatitis virus (VSV) is synthesized on membrane‐bound polyribosomes. Approximately 30 min after its synthesis, it reaches the surface plasma membrane where it is incorporated into budding virus. The first part of this paper focuses on the 2 intracellular, mimbrane‐bound, glycosylated forms of the glycoprotein which are intermediates in its biogenesis. All glycosylation and processing is completed in the smooth microsome fraction before the protein reaches the surface.Next, we turn to the mechanism by which G is synthesized on membrane‐bound polyribosomes. All of the G mRNA is bound to membranes, and studies with puromycin suggest that this attachment of G mRNA is mediated by the nascent glycoprotein chain. After its synthesis G is a transmembrane protein with about 30 amino acids at the carboxyl terminus remaining on the cytoplasmic side of the endoplasmic reticulum. Since 95% of the glycoprotein, containing the carbohydrate residues, is resistant to attack by external proteases, it appears to be within the lumen of the endoplasmic reticulum or embedded within the lipid bilayer. Finally, we show that synthesis, glycosylation, and proper asymmetric insertion of G into the ER can be achieved in cell‐free extracts. Both glycosylation of G and proper insertion into the ER membrane in this cell‐free system require concomitant protein synthesis.
Comparison of the carbohydrate of sindbis virus glycoproteins with the carbohydrate of host glycoproteins
Authors: Keegstra Kenneth , Burke David 
Published: May 2005

AbstractThe carbohydrate portions of the Sindbis virus glycoproteins were compared with the carbohydrate portions of cell surface glycoproteins from uninfected host cells. Comparisons of the size of glycopeptides were made using gel filtrations. Comparisons of sugar linkages were made by methylation analysis. The conclusion was that the Sindbis carbohydrate is similar to a portion of the host carbohydrate. Thus, the Sindbis carbohydrate structures appear to be structures normally made in the uninfected host cell, but which are added to the Sindbis glycoproteins in virus‐infected cells.
Synthesis, secretion, and attachment of lets glycoprotein in normal and transformed cells
Authors: Hynes Richard O. , Destree Antonia T. , Mautner Vivien M. , Ali Iqbal U. 
Published: May 2005

AbstractLETS glycoprotein is a surface glycoprotein which is absent or greatly diminished on the surfaces of transformed cells. Normal cells secrete large amounts of this protein into the medium; transformed cell medium contains much less. The difference is not due to degradation of the soluble LETS protein. Biosynthesis of LETS protein can be studied by analysis of cell extracts by detergent extraction and immune precipitation and appears to proceed in transformed cells at a reduced rate compared with normal cells. Addition of inhibitors of protein synthesis to transformed cell cultures causes the small amount of LETS protein in the medium to attach to the cells. Addition of normal conditioned medium, which contains LETS protein, to transformed cells alters their morphology towards normal. Addition of purified LETS protein to transformed cells causes the cells to attach, spread, align with one another, and regain actin cables. The results indicate that LETS protein can exchange between cell surface and medium and that it affects cellular adhesion, morphology, and cytoskeleton.
Enzymatic conversion of proteins to glycoproteins by lipid‐linked saccharides: A study of potential exogenous acceptor proteins
Authors: Kronquist Kathryn E. , Lennarz William J. 
Published: May 2005

AbstractPrevious studies have shown that a membrane preparation from hen oviduct catalyzes transfer of oligosaccharide from oligosaccharide‐P‐P‐dolichol to denatured RNase and α‐lactalbumin. To gain further insight into the structural requirements of a protein that allow it to serve as a substrate for glycosylation, the acceptor ability of a variety of other modified proteins containing the tripeptide sequence ‐ASN‐X‐(SER/THR)‐ has been investigated. Of 7 proteins tested, 2 (ovine prolactin and rabbit muscle triosephosphate isomerase) could be enzymatically glycosylated by a particulate preparation from hen oviduct. The remaining 5 proteins, assayed as either S‐carboxy‐methylated or S‐aminoethylated derivatives, were inactive as carbohydrate acceptors. However, cyanogen bromide treatment of 2 of the inactive proteins, bovine catalase and concanavalin A from jack bean, yielded peptide fragments which served as substrates for glycosylation. These results suggests that for some proteins, disruption of the tertiary structure is sufficient to allow attachment of carbohydrate. Other denatured proteins may possess additional restrictions imposed by their secondary structure. In certain cases, these restrictions are removed when the polypeptide chain is fragmented.
Inhibition of the binding of low‐density lipoprotein to its cell surface receptor in human fibroblasts by positively charged proteins
Authors: Brown Michael S. , Deuel Thomas F. , Basu Sandip K. , Goldstein Joseph L. 
Published: May 2005

AbstractA group of proteins and polyamino acids with positively charged domains were shown to inhibit the binding of 125I‐LDL to its receptor on the surface of human fibroblasts. The list of inhibitory proteins included platelet factor 4 (which has a cluster of lysine residues at its carboxyl terminus), two lysinerich histones, poly‐L‐lysines of chain length greater than 4, and protamine. These proteins were effective in the concentration range of 5–50 μg/ml. Two other positively charged proteins, lysozyme and avidin, did not inhibit 125I‐LDL binding. Kinetic studies suggested that protamine was not acting simply as a competitive inhibitor with regard to the LDL receptor. In light of previous data showing that polyanions such as heparin and polyphosphates also inhibit 125I‐LDL binding to its cell surface receptor, the current findings suggest that charge interactions are important in this binding reaction. In a related series of studies, a number of glycoproteins and their asialo derivatives as well as a number of sugar phosphates failed to inhibit 125I‐LDL binding to its receptor in fibroblasts.
Physical‐chemical studies of spectrin
Authors: Ralston G. B. 
Published: May 2005

AbstractIn recent years considerable progress has been made in the understanding of the structure and function of the red blood cell membrane. The protein spectrin, of high molecular weight and propensity for self‐association, appears to play a major role, in concert with actin, in maintaining the shape and integrity of the membrane. A study of the physical‐chemical properties of spectrin, and its size, shape, self‐association pattern, and its interaction with other components, leads to a plausible model for the way this protein performs its biological role. The evidence from the structure and interactions of spectrin suggests a structure which is relatively symmetrical yet highly expanded, and which allows extensive, two‐dimensional network formation with actin. In these respects, the structure of spectrin is quite different from that of myosin, to which it has often been likened.
The exchangeability of human erythrocyte membrane cholesterol
Authors: Lange Yvonne , D'Alessandro Josephine S. 
Published: May 2005

AbstractA new method has been used to determine what fraction of human erythrocyte cholesterol is available for exchange with plasma unesterified cholesterol. Erythrocytes labeled with 3H‐cholesterol by this exchange process were incubated with sonicated phosphatidylcholine vesicles, giving rise to a net movement of cholesterol out of the cells. The specific activity of cholesterol taken up by the vesicles depended on the length of time of incubation. Initially the specific activity in the vesicles was greater than that in the cells, but after approximately 10% of cell cholesterol had been removed, the specific activity of subsequently removed cholesterol was equal to that of the remaining erythrocyte cholesterol. We conclude from these data that (a) all of the cholesterol in the erythrocyte is exchangeable with plasma, and (b) approximately 10% of erythrocyte cholesterol is in a more rapidly exchangeable pool than the remainder.
Beta‐adrenergic receptors: Regulatory role of agonists
Authors: Lefkowitz Robert J. , Limbird Lee E. , Williams Lewis T. , Wessels Michael 
Published: May 2005

AbstractDirect radioligand binding studies have been used to probe the molecular mechanisms whereby agonist catecholamines regulate the function of betaadrenergic receptors in a model system, the frog erythrocyte. The unique characteristics of agonist as opposed to antagonist action are first, the ability to stimulate the adenylate cyclase through the receptor and second, the ability to desensitize the system by alterations induced in beta‐adrenergic receptors. These properties of agonist are not shared by antagonist despite the high affinity and specificity of antagonist binding to the beta‐adrenergic receptors. Agonist and antagonist receptor complexes may be distinguished in a variety of ways including differences in their sensitivity to regulatory guanine nucleotides and also by gel chromatography on AcA 34 Ultragel. The agonist receptor complex appears to elute from the columns with an apparently increased size. A “dynamic receptor affinity model” of beta‐adrenergic receptor action is proposed which features several distinct conformational states of the receptor. Agonists have much higher affinity for the physiologically active or coupled state of the receptor, whereas antagonists have equal affinity for both. In addition, a third “desensitized” state of the receptor is also postulated to exist.
Effects of abnormal cation transport on deformability of desiccytes
Authors: Clark Margaret R. , Mohandas Narla , Caggiano Vincent , Shohet Stephen B. 
Published: May 2005

AbstractWe have studied the deformability of subpopulations of red cells from a patient with “desiccytosis”, a disorder characterized by increased membrane permeability to potassium and associated with a probable increase in sodium‐sodium exchange. Cells become increasingly dehydrated after maturation because of continued potassium loss without compensatory sodium gain, and they exhibit a progressive increase in mean cell hemoglobin concentration (MCHC). This increase in MCHC causes the cells to become undeformable at shear stress values which result in extensive deformation of normal cells. Reduction of MCHC to approximately normal levels by suspending the cells in hypotonic medium restores normal deformability to all but 0.1–0.2% of the cells. These results suggest that the major factor leading to premature destruction in this disorder is whole cell rigidity conferred by increased intracellular hemoglobin concentrations, rather than any associated membrane rigidity.
Erythrocyte troponin inhibitor‐like protein: Isolation and characterization
Authors: Maimon Jonathan , Puszkin Saul 
Published: May 2005

AbstractA protein was isolated from a human erythrocyte lysate with an apparent molecular weight of 23,000–24,000 daltons. This protein was purified by batch DEAE cellulose followed by column DEAE cellulose chromatography and a gradient of NaCl. On sodium dodecyl sulfate acrylamide electrophoresis, the erythrocyte protein comigrated with muscle troponin inhibitor. An isoelectric precipitation (pH 9.25) was used for the separation of muscle troponin inhibitor from a complex with another troponin component. Both the erythrocyte protein and the muscle troponin inhibitor partially inhibited muscle myosin Ca2+ and K+‐EDTA ATPase activity. Furthermore, they inhibited actin‐activated Mg2+‐ATPase of muscle myosin. The inhibitory effects were absent in the presence of muscle troponin calcium‐binding component. Muscle troponin inhibitor and the erythrocyte troponin inhibitor‐like protein bound to muscle myosin when myosin was precipitated twice at low ionic strength. The presence of a troponin inhibitor‐like protein in erythrocytes suggests that it may be a component in the regulation of contractile activity.
Spin label studies on rat liver and heart plasma membranes: Effects of temperature, calcium, and lanthanum on membrane fluidity
Authors: Gordon Larry M. , Sauerheber Richard D. , Esgate Judy A. 
Published: May 2005

AbstractThe structures of rat liver and heart plasma membranes were studied with the 5‐nitroxide stearic acid spin probe, I(1 2,3). The polarity‐corrected order parameters (S) of liver and heart plasma membranes were independent of probe concentration only if experimentally determined low I(1 2,3)/lipid ratios were employed. At higher probe/lipid ratios, the order parameters of both membrane systems decreased with increasing probe concentration, and these effects were attributed to enhanced nitroxide radical interactions. Examination of the temperature dependence of approximate and polarity‐corrected order parameters indicated that lipid phase separations occur in liver (between 19° and 28°C) and heart (between 21° and 32°C) plasma membranes. The possibility that a wide variety of membrane‐associated functions may be influenced by these thermotropic phase separations is considered.Addition of 3.9 mM CaCl2 to I(1 2,3)‐labeled liver plasma membrane decreased the fluidity as indicated by a 5% increase in S at 37°C. Similarly, titrating I(1 2,3)‐labeled heart plasma membranes with either CaCl2 or LaCl3 decreased the lipid fluidity at 37°C, although the magnitude of the La3+ effect was larger and occurred at lower concentrations than that induced by Ca2+; addition of 0.2 mM La3+ or 3.2 mM Ca2+ increased S by approximately 7% and 5%, respectively. The above cation effects reflected only alterations in the membrane fluidity and were not due to changes in probe–probe interactions. Ca2+ and La3+ at these concentrations decrease the activities of such plasma membrane enzymes as Na+, K+‐ATPase and adenylyl cyclase, and it is suggested that the inhibition of these enzymes may be due in part to cation‐mediated decreases in the lipid fluidity.
Transmembrane interactions and the mechanisms of transport of proteins across membranes
Authors: Singer S. J. , Ash J. F. , Bourguignon Lilly Y. W. , Heggeness Michael H. , Louvard Daniel 
Published: May 2005

AbstractWe have made observations, by double fluorescence staining of the same cell, of the distributions of surface receptors, and of intracellular actin and myosin, on cultured normal fibroblasts and other flat cells, and on lymphocytes and other rounded cells. The binding of multivalent ligands (a lectin or specific antibodies) to a cell surface receptor on flat cells clusters the cell receptors into small patches, which line up directly over the actin‐ and myosin‐containing stress fibers inside the cell. Similar ligands binding to rounded cells can cause their surface receptors to be collected into caps on the surface, and these caps are invariably found to be associated with concentrations of actin and myosin under the capped membrane. Although these ligand‐induced surface phenomena appear to be different on flat and rounded cells, we propose that in both cases clusters of receptors become linked across the membrane to actin‐ and myosin‐containing structures. In flat cells these structures are very long stress fibers; therefore, when clusters of receptors become linked to these fibers, the clusters are immobilized. In round cells, membrane‐associated actin‐ and myosin‐containing structures are apparently much less extensive than in flat cells; therefore, clusters of receptors linked to these structures are still mobile in the plane of the membrane. We suggest that in this case the clusters are then actively collected into a cap by an analogue of the muscle sliding filament mechanism.To explain the transmembrane linkage, we propose that actin is associated with the plasma membrane as a peripheral protein which is directly or indirectly bound to an integral protein (or proteins) X of the membrane. Individual molecules of any receptor are not bound to X, but after they are specifically clustered into patches, a patch of receptors then becomes bound to S and hence to actin/myosin.Patching and capping of specific receptors on rounded cells is often accompanied by a specific endocytosis of the ligand‐receptor complexes. This represents one common transport mechanism of a protein (the ligand) across the plasma membrane. The possibility is discussed that this type of endocytosis is mediated by a transmembrane linkage of the clustered receptor to actin/myosin. Another mechanism of endocytosis involves the “coated pit” structures that are observed by electron microscopy of plasma membranes. The possible relationships between an actin/myosin and a coated pit mechanism of endocytosis are explored.
Bilayer balance and regulation of red cell shape changes
Authors: Mohandas Narla , Greenquist Alfred C. , Shohet Stephen B. 
Published: May 2005

AbstractDiscocytic human red cells undergo discocyte‐echinocyte and discocytestomatocyte transformations under the action of a wide variety of lipid‐soluble anionic and cationic agents respectively. These shape transformations are explained by the bilayer couple hypothesis of Sheetz and Singer to be the result of preferential distribution of the anionic agents in the outer half of the bilayer and the cationic agents in the inner half of the bilayer. We demonstrate that echinocytogenic effects indeed occur when the naturally occurring phospholipid lysophosphatidylcholine (LPC) is localized in the outer half of the bilayer, and stomatocytogenic effects occur when LPC is in the inner half. However, in contrast to the bilayer couple hypothesis, our results show that simple equivalent membrane surface area expansion on each layer is insufficient to maintain the discocytic shape and there exists a differential concentration effect of LPC on the two halves of the bilayer.