Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Peptides of glycophorin AMN were prepared by cyanogen bromide cleavage and by chymotryptic and tryptic digestion. Cyanogen bromide cleavage produces three fragments which account for the entire polypeptide chain. Trypsin and chymotrypsin cleave completely at several sites, but incompletely at sites within the glycosylated segment of the polypeptide chain. Some of the latter sites become accessible to proteolysis after desialation in addition to exposure of new sites for cleavage. The amino acid sequence of glycophorin AMN has been determined by manual Edman degradation, using both the direct Edman and the dansyl-Edman procedures simultaneously for determination of glycosylated amino acid residues. The automated procedure was used for sequence determination of a hydrophobic peptide. Glycophorin A is a polypeptide chain of 131 amino acid residues and contains 16 oligosaccharide units attached to the amino-terminal third of the molecule. Fifteen oligosaccharides are linked O-glycosidically to either threonine or serine residues and one complex oligosaccharide unit is attached N-glycosidically to an asparagine residue. Amino-terminal sequences are different for glycophorin AM and AN, the two forms of the glycophorin A molecule coded for by genes at the MN locus. The differences in sensitivity to proteases of various sites on glycophorin A seem to be due to heterogeneity in the carbohydrate components and not to differences in the primary structure of the polypeptide chains. This work contains a number of revisions and corrections of earlier preliminary reports [Segrest, J.P., Jackson, R. chem. Biophys. Res. Commun, 49, 964-969; Tomita, M., & Marchesi, V.T. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 2964-2968].
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PMID:Primary structure of human erythrocyte glycophorin A. Isolation and characterization of peptides and complete amino acid sequence. 72 84

Three disulfide-linked peptides with molecular weights of about 6000, 7000 and 45000, respectively, were isolated from bovine fibrinogen cleaved with cyanogen bromide. The chain constituents of these peptides were separated after reduction and alkylation and identified by partial amino acid sequence analysis. Of the five polypeptide chains of the largest fragment F-CB2, three are derived from the central region of Bbeta chain, one from the Aalpha chain and one from the gamma chain. The smaller peptides F-CB4 and F-CB5 consist of one and two polypeptide chains and originate from central regions of the Bbeta and gamma chains, respectively, indicating that they represent intrachain disulfide loops. These and previous data show that the disulfide-bonded regions of bovine fibrinogen are similar to those in human fibrinogen.
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PMID:Disulfide-linked cyanogen bromide peptides of bovine fibrinogen. III. Isolation and identification by sequence analysis of the chain constituents in peptides F-CB2, F-CB4 and F-CB5. 73 Jan 13

beta1-Bungarotoxin modified with p-bromophenacyl bromide (BPB) was reduced and carboxymethylated, and the resulting two constituent RCM-polypeptide chains (the RCM-A and B chains) were separated. The RCM-A chain was found to be modified by BPB by measuring its UV absorption spectrum and was shown to have lost one histidine residue by analyzing its amino acid composition. To determine the location of the modified histidine residue in the A chain of the toxin, the RCM-A chain was digested with TPCK-trypsin, and the resulting peptides were fractionated by gel filtration followed by DEAE-cellulose chromatography. The modified residue was finally identified as histidine-48 in the A chain by Edman degradation and from the amino acid composition of the BPB-modified peptide. The amino acid sequence around the modified histidine residue in the A chain is highly homologous with those of porcine pancreas phospholipase A2 and presynaptic toxin, notexin. We conclude that histidine-48 in the A chain participates in the phospholipase A activity of beta1-bungarotoxin.
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PMID:Characterization of phospholipase A activity of beta1-bungarotoxin from Bungarus multicinctus venom. II. Identification of the histidine residue of beta1-bungarotoxin modified by p-bromophenacyl bromide. 73 Jul 54

Previous studies have shown that a membrane preparation from hen oviduct catalyzes transfer of oligosaccharide from oligosaccharide-P-P-dolichol to denatured RNase and alpha-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-carboxymethylated 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.
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PMID:Enzymatic conversion of proteins to glycoproteins by lipid-linked saccharides: a study of potential exogenous acceptor proteins. 73 7

The determination of the amino acid sequence of the dihydrofolate reductase (EC 1.5.1.3) from cells of the mouse lymphoma L1210 is described. The protein was cleaved by cyanogen bromide to produce the six fragments CB1 (residues 1 to 14), CB2 (residues 15 to 52), CB3 (residues 53 to 111), CB4 (residues 115 to 125), CB5 (residues 126 to 139), and CB6 (residues 140 to 186). One of the fragments, CB2, contained an internal homoserine derived from a methionine which was not cleaved by cyanogen bromide. The amino acid sequences and order of the cyanogen bromide fragments were determined by a combination of automatic and manual sequence analyses of the fragments and small peptides from tryptic, thermolytic, and Staphylococcus aureus protease digestions. The complete sequence comprises 186 residues in a single polypeptide chain of molecular weight 21,458. Comparison of the sequence of the L1210 dihydrofolate reductase with the sequences of the enzymes from Streptococcus faecium, escherichia coli RT500, and Lactobacillus casei indicates that all enzymes show some homology, which is strongest in the regions forming the substrate binding cleft.
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PMID:The amino acid sequence of dihydrofolate reductase from the mouse lymphoma L1210. 76 74

The complete amino acid sequence has been derived for human C-reactive protein (CRP). The protein yielded a unique sequence containing 187 amino acids in a single polypeptide chain. The NH2-terminal residue of CRP is pyrrolidonecarboxylic acid and the COOH terminus is proline. The 2 half-cystine residues at positions 36 and 78 are involved in a disulfide bond. Based on the amino acid composition derived from the sequence data, a minimal molecular weight of 20,946 has been calculated for human CRP. This value agrees well with the molecular weight of 21,500 established by gel filtration of CRP in 5.0 M guanidine Cl (Gotschlich, E.C., and Edelman, G.M. (1965) Proc. Natl. Acad. Sci. U.S.A. 54, 558--566). The primary structure of human CRP has been examined for internal homology and compared to all known proteins whose structures were published before April, 1978 by two computer programs; program SEARCH and program RELATE (Dayhoff, M. O., ed (1976) in Atlas of Protein Sequence and Structure, Vol. 5, Suppl. 2, pp. 3--8, National Biomedical Research Foundation, Silver Spring, MD). The computer analyses showed no significant repeating sequences within the C-reactive protein molecule. This observation seems to rule out the possibility of gene duplication in the evolution of this protein. Distant homologies, which were statistically insignificant, have been noted to the CH2 domain of immunoglobulin G (IgG) and to C3a anaphylotoxin. The homologie noted are insufficient to support a common evolutionary origin of these proteins. No homology region in other heavy chains was observed. It is therefore preferable, at this point in time, to assign CRP and the protein known as 9.5 S alpha-glycoprotein, P component, and Clt to a new super family unrelated to any other proteins investigated. The homology between these proteins was demonstrated previously (Osmand, A.P., Friedenson, B., Gewurz, H., Painter, R.H., Hofmann, T., and Shelton, E. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 739--743) on the basis of sequence data on approximately 20 NH2-terminal residues of rabbit C-reactive protein, of Clt, and a cyanogen bromide fragment of human CRP.
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PMID:Primary structure of human C-reactive protein. 76 75

One of the major proteins of the Escherichia coli outer cell envelope membrane, protein I, can be separated electrophoretically into protein components Ia and Ib. Strain differences exist regarding presence or absence of component Ib and this component can selectively be lost by mutation to resistance against a phage. Both components Ia and Ib are further heterogeneous isoelectrically, and both together may contain at lease six separable isoelectric species. As judged by analysis of their cyanogen bromide fragments, Ia and Ib are almost identical concerning their primary structure; the difference (charge only or size and charge) was located in a part of the protein that does not correspond to the C-terminal or N-terminal regions. Components Ia and Ib thus represent essentially the same polypeptide and they may arise by a modification process in vitro or the existence of two almost identical genes.
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PMID:The major proteins of the Escherichia coli outer cell-envelope membrane. Heterogeneity of protein I. 77 Jan 69

Kinetic properties of protein methylase II (S-adenosymethionine:protein O-methyltransferase, EC 2.1.1.24) which methylates (esterifies) the free carboxyl side chains of amino acids in proteins was studied using various polypeptides as methyl acceptor substrates. Bovine pancreatic ribonuclease, a model substrate for the enzyme, was subjected to specific cleavage by cyanogen bromide, trypsin, and performic acid oxidation. Several polypeptide fragments derived were then separated by molecular sieve chromatography on a column of Sephadex G-25. The method was found to be very simple and gave good yields. Km values for these polypeptides as well as a few other protein substrates were determined. While Km values for the isolated peptides range generally between 4.8 and 0.7 X 10-3 M, those of native bovine panreatic ribonuclease, luteinizing hormone, and follicle-stimulating hormone were determined to be 4.0 X 10-4, 5.0 X 10-5, and 0.77 X 10-5, respectively. Sites of enzymatic methylation of the native ribonuclease were also investigated. Although polypeptides derived from the C-terminal and N-terminal regions of the molecule were found to accept methyl groups, they were unable to under go enzymatic methylation when native molecule was used as the substrate indicating that within the native ribonuclease these regions are in a conformation which do not allow them to be methylated by protein methylase II under the present assay conditions.
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PMID:A comparison of kinetic parameters of polypeptide substrates for protein methylase II. 78 14

HLA antigens are coded for by three closely linked loci. The gene products of the first and second locus are known to be very similar in overall structure. Antigens coded for by the third locus were examined with regard to their chemical and immunological relationship to the first and second loci gene products. It is demonstrated that the third locus antigens are composed of two types of polypeptide chains, the smaller of which is identical to beta2-microglobulin. The alloantigenic polypeptide chain has an apparent molecular weight of 48 000 when solubilized by detergen treatment and about 35 000 when released from the cell membrane by proteolysis. These data together with size and shape analyses by gel chromatography and sedimentation velocity determinations show that HLA antigens from the three subloci are indistinguishable with the techniques employed. Suggestive evidence was obtained that the third locus antigens are more sensitive to proteolysis than the first and second locus antigens. The similarity between the three gene products was also evident on cyanogen bromide fragmentation of the polypeptide chains. Furthermore, rabbit antibodies against antigens coded for by the first locus cross-reacted extensively with antigens from the second and third locus. This study therefore lends strong credence to the view that the three HLA antigen subloci have arisen by gene duplications of a common ancestral gene.
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PMID:Structural and immunological similarities between HLA antigens from three loci. 78 99

The cyanogen bromide cleavage of "acetic" polyhedral protein from nuclear polyhedrosis virus of B. mori was performed. Two peptides BrCN-II and BrCN-II' which consist of 29 and 34 amino acid residue were isolated from a mixture of cyanogen bromide fragments. The amino acid composition and N-terminal amino acids were established. The tryptic proteolysis of these fragments was conducted and the tryptic peptides were separated. The amino acid composition of tryptic peptides was determined. The data obtained make it possible to consider these fragments to be internal areas of polypeptide chain of the protein under investigation.
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PMID:[Isolation and characteristics of fragments from the cyanogen bromide splitting of inclusion body proteins of Bombyx mori nuclear polyhedrosis virus]. 79 77


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