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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acetylcholine receptors of fish electric organs and mammalian skeletal muscle comprise four structurally homologous glycoprotein subunits in the mole ratio alpha 2 beta gamma delta (refs 1-4). All four subunits have leader sequences and are exposed on both sides of the membrane. From amino acid sequencing, three groups have predicted that each subunit has four hydrophobic alpha-helical transmembranous domains. Because the N-terminus of each subunit is thought to remain on the extracellular surface after cleavage of the leader sequence, this model predicts that the N- and C- termini are both on the extracellular side. An alternative model proposed by two other groups predicts that there is, in addition, a fifth amphipathic transmembranous domain which would place the C-terminus on the cytoplasmic side. Here, using anti-subunit sera and monoclonal antibodies and their reaction with synthetic subunit peptides, we demonstrate that the C-terminus is in fact on the cytoplasmic surface. We also show that, contrary to other predictions, the most hydrophilic sequence on the extracellular domain of alpha-subunits is not the main immunogenic region.
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PMID:Immunochemical tests of acetylcholine receptor subunit models. 620 39

The vesicular stomatitis virus glycoprotein reconstituted into dipalmitoylphosphatidylcholine (DPPC) vesicles exerts a profound effect upon the DPPC gel to liquid-crystalline phase transition. The glycoprotein was reconstituted into DPPC vesicles by octyl glucoside dialysis. The gel to liquid-crystalline phase transition of these vesicles was monitored by differential scanning calorimetry. Vesicles formed in the absence of glycoprotein (600--2100-A diameter) underwent the phase transition at 41.0 degrees C and had an associated enthalpy change of 8.0 +/- 1.6 kcal/mol. Increasing the mole ratio of glycoprotein to DPPC in the vesicles to 0.15 mol % reduced both the transition temperature and the transition enthalpy change. The enthalpy change as a function of the mole percent glycoprotein could be fit to a straight line by a least-squares procedure. Extrapolation of the results to the glycoprotein concentration where the enthalpy change was zero indicated one glycoprotein molecule bound 270 +/- 150 molecules of DPPC.
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PMID:Thermotropic behavior of dipalmitoylphosphatidylcholine vesicles reconstituted with the glycoprotein of vesicular stomatitis virus. 624 46

The mole-rat, Spalax ehrenbergi, is a complex subterranean rodent species whose habitat is restricted largely to the Middle East and North Africa. We typed over 50 mole-rats with mouse monoclonal and polyclonal antibodies specific for class I and class II major histocompatibility complex (Mhc) molecules. Some of these antibodies were produced against mouse Mhc molecules, others against Mhc molecules of other species. About 25% of the antibodies reacted with mole-rat lymphocytes in the cytotoxic test. Some of the serologically positive antibodies precipitated from a glycoprotein pool of mole-rat spleen cell molecules that corresponded in size with class I and class II molecules of other species. We conclude, therefore, that mole-rats, like other mammals, possess the Mhc which consists of class I and class II loci. We call this Mhc Spalax major histocompatibility (Smh) complex. The occurrence of a large number of different serotypes among the tested animals suggests that Smh loci are polymorphic. This Mhc polymorphism of the mole-rat contrasts with the monomorphism or oligomorphism of the Syrian hamster, a rodent with a similar ecology. Thus far no qualitative correlation could be found between Smh polymorphism and chromosome variation described in this superspecies.
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PMID:Major histocompatibility complex of the mole-rat. I. Serological and biochemical analysis. 638 77

When 125I-labeled thrombin was incubated with washed human platelets or with the supernatant solution of activated platelets, it formed a NaDodSO4-stable complex of apparent mass greater than 450 000 daltons. Formation of the complex was temperature dependent; with 20 nM thrombin incubated with the supernatant solution of ionophore-activated platelets, the initial rate of formation of the stable complex was 1 nM thrombin/min at 37 degrees C, 50 times the rate at 22 degrees C. Thrombin with all free amino groups methylated was still reactive. Active-site-blocked thrombin formed the complex only slowly. The complex that formed with active thrombin was not dissociated by hydroxylamine in urea. Reduction with 2-mercaptoethanol dissociated the complex, and its formation was blocked by the sulfhydryl-blocking agents iodoacetamide and 4,4'-dithiodipyridine. The complex was thus unlike those of thrombin and alpha 2-macroglobulin or antithrombin III, but it had characteristics of a disulfide-linked complex. Of the secreted proteins, albumin and glycoprotein G adhered to an activated thiol-Sepharose column, indicating that they contained free thiol groups. Purified glycoprotein G and thrombin formed a complex similar to the complex formed when thrombin was incubated with the supernatant solution of activated platelets. The purified glycoprotein bound 2.6 mol of radioactive N-ethylmaleimide/mol of protein, indicating three sulfhydryl groups per mole. After reacting with purified glycoprotein G, thrombin developed a new sulfhydryl group. It is concluded that glycoprotein G (thrombin-sensitive protein, thrombospondin) and thrombin form a dissociable complex that leads to a covalent complex by thiol-disulfide exchange of a thiol group on glycoprotein G and a disulfide on thrombin.
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PMID:Formation of a stable complex of thrombin and the secreted platelet protein glycoprotein G (thrombin-sensitive protein, thrombospondin) by thiol-disulfide exchange. 643 45

Many melanoma-associated antigens have been identified by monoclonal antibodies. One of these monoclonal antibodies, O1-94-45, binds only to melanomas, nevus cells, some astrocytomas, and fetal epitheloid cells. There are approximately 100,000 cell surface antigens per melanoma cell with an association constant of 3 X 10(8) M-1. The antigen is efficiently extracted from the membrane only in the presence of detergent and is, therefore, bound by hydrophobic forces. However, it is also shed into the culture supernatant during normal cell growth. The two components of the O1-95-45 antigen are a chondroitin sulfate proteoglycan (CSP, greater than 500,000 Da) and a glycoprotein gp260 (260,000 Da, pI 6.9). CSP contains chondroitin sulfate and N-linked and O-linked oligosaccharides. Only N-linked saccharides were associated with gp260. The antigenic site is expressed on both components and is heat-sensitive. Since the CSP was converted to gp260 by chondroitinase, the protein cores of the two molecules are the same or similar. For more detailed study the O1-95-45 antigen was purified by immunoaffinity chromatography. The amino acid composition of the purified antigen was relatively polar with an unusually high Leu content and low Lys content. Initial attempts to sequence the antigen were unsuccessful probably due to a blocked N-terminus. CSP and gp260 were partially separated by gel filtration chromatography, and both were found to carry the O1-95-45 antigenic determinant. Three other monoclonal antibodies were found to bind the purified antigen at a site or sites different from the O1-95-45 epitope and one other monoclonal antibody may bind at the same site. Two of these antibodies were used for a double determinant immunoassay.
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PMID:Isolation and chemical characterization of a melanoma-associated proteoglycan antigen. 661 28

Extensive succinylation of 19 S normal human thyroglobulin having a high iodine content results in the formation of a 26,000-Da peptide. One-half mole of the peptide is obtained from 1 mol of the high molecular weight glycoprotein. The dissociation of the peptide is accompanied by the appearance of an intense absorption band which has a maximum at 264 nm. The absorption band is associated exclusively with the 26,000-Da peptide. The amino acid composition of the peptide differs from 19 S thyroglobulin by having no cysteine and higher contents of serine, alanine, tyrosine, phenylalanine, lysine, glycine, isoleucine, and histidine. The peptide also has a high thyroxine content. There were no detectable carbohydrates in the peptide. The fluorescence spectrum of the 26,000-Da peptide shows an emission maximum at 405 nm which we have recently assigned to iodotyrosine-iodotyrosine interactions (Shifrin, S., Consiglio, E., and Kohn, L. D. (1983) J. Biol. Chem. 258, 3780-3786). A 26,000-Da peptide with the same physicochemical properties is found in extracts of normal human thyroid glands.
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PMID:Noncovalent interactions of a 26,000-dalton peptide with 19 S human thyroglobulin. 663 Feb

The interaction of the human erythrocyte concanavalin A receptor (a subpopulation of Band 3) with phospholipids has been investigated using differential scanning microcalorimetry of reconstituted vesicles prepared by detergent dialysis. The mean diameter of dialyzed phospholipid vesicles jumps dramatically on inclusion of the concanavalin A receptor and then increases linearly with the fraction of protein in the bilayer. The glycoprotein has a dramatic effect on the phospholipid gel to liquid-crystalline phase transition, and delta H decreases linearly with increasing mole fraction of protein up to a protein/lipid mole ratio of around 1:1160. Extrapolation of this data indicates that each concanavalin A receptor is able to perturb about 685 molecules of dimyristoylphosphatidylcholine, withdrawing them from the main phase transition. The cooperativity of phospholipid melting is profoundly disrupted by small amounts of glycoprotein, with the cooperative unit dropping to less than half its initial values at a protein/lipid mole ratio of 1:3800. A break occurs in the delta H curve as the protein/lipid mole ratio is increased above 1:1160, and delta H then increases linearly with increasing amounts of concanavalin A receptor in the bilayer. This phenomenon may be interpreted in terms of protein-protein aggregation which occurs in the phospholipid bilayer above a certain critical mole fraction of concanavalin A receptor, resulting in perturbed phospholipids being returned to the phase transition. In addition, the hydrophilic domains of the glycoprotein may exist in two different conformations depending on the protein concentration in the bilayer, and these may differ in their ability to interact with phospholipid headgroups at the membrane surface.
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PMID:Lipid-protein interactions of the human erythrocyte concanavalin A receptor in phospholipid bilayers. 673 2

Surface charges of isolated neurons of rat dorsal root ganglion were studied by the microelectrophoresis. It was shown that the surface potential of these neurons is produced by anion groups which form complexes with calcium ions and a binding constant ranging from 10 to 50 1/mole; they can be titrated by hydrogen ions according to pK = 3.8. Under trypsin treatment the surface loses most of these groups. Tosylchloride (reagent for aminogroups ) slightly increases the surface charge and N- bromsuccinimide (reagent for carboxylic groups) partially neutralizes it. It is suggested that the surface charge of rat dorsal root ganglion neurons measured by the microelectrophoresis is mainly determined by carboxylic groups of periphery proteins. These groups seem to be located in the glycoprotein sheath which covers the outer surface of the membrane. According to our estimates the average distance between these groups is about 2 nm and the thickness of the sheath is about 10 nm.
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PMID:[Study of the surface properties of spinal ganglion neurons in the rat by the microelectrophoresis technic]. 673 45

The measurement of the affinity of anti-HBs antibody in human sera using 3 HBsAg-related antigens is described. The antigens used were (i) a synthetic linear peptide corresponding to amino acids 139-147 of the major polypeptide of HBsAg, (ii) a cyclical form of this same peptide and (iii) a polypeptide complex of a 28,000 MW glycoprotein and a 23,000 MW protein from purified HBsAg. The method was established with a pooled human anti-HBs immunoglobulin preparation and a monoclonal anti-HBs antibody reactive to the 'a' determinant of HBsAg. The results indicate that both these antibody preparations effectively bind the 3 antigens with affinity values of between 2 X 10(6) to 9 X 10(7) litres/mole. However, the affinity of both antibody preparations for the cyclical form of the peptide was higher than for the linear form. The level of antibody (expressed as Abt, molar antigen binding sites) in the pooled human immunoglobulin for each of the 3 antigens was similar. Measurements of anti-HBs antibodies in the sera of recovered acute hepatitis B patients and from HBsAg negative chronic liver disease patients showed that the cyclical form of the antigen was bound with a higher affinity than the linear form. Affinity values of antibody in the sera of the latter group of patients was significantly lower (3 X 10(5) to 2.7 X 10(6) litres/mole) than those observed in sera from other individuals. The implication of these results in determining the importance of the measurement of affinity in the assessment of the efficacy of vaccines is discussed.
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PMID:Determination of the affinity of antibodies to hepatitis B surface antigen in human sera. 674 4

A procedure for the isolation of the human complement (C) protein C9 is described. The procedure allowin. The purified protein has the electrophoretic mobility of an alpha-globulin, and is a single polypeptide chain with a m.w. of 71,000. No impurities were detected either on gel electrophoretic or immunochemical examination. C9 is a glycoprotein containing 7.8% carbohydrate, and in terms of residues per mole, 3.0 glucosamine, 17.6 neutral hexose, and 7.4 sialic acid. Its amino acid composition is typical of a globular serum protein. Upon automated Edman degradation of reduced and alkylated C9, no amino acid residues were released, suggesting a blocked N-terminus. The concentration of C9 in normal human serum is 58 +/- 8 microgram/ml. A high titer rabbit antiserum was produced and employed to immunochemically deplete serum of C9. The CH50 of the C9-depleted serum was identical to that of whole human serum; however, membrane fragments of erythrocytes lysed by C9-depleted serum lacked the typical ultrastructural C lesions, which constitute the dimeric membrane attack complex.
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PMID:The ninth component of human complement: purification and physicochemical characterization. 676 71


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