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)

Rat and human neutrophil N-formyl-peptide chemotactic receptors were subjected to glycosidase and proteinase treatments to determine the extent and species differences of glycosylation and the carbohydrate requirement in the high-affinity ligand binding. N-Formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys was attached to rat and human neutrophils either before or after glycosidase and proteinase treatments, and the labelled receptors were solubilized after glutaraldehyde cross-linking and analysed by SDS/PAGE and autoradiography. Both the rat and human N-formyl-peptide chemotactic receptors contain only N-linked oligosaccharides, as demonstrated by their sensitivity to peptide N-glycosidase F (PNGase F) and resistance to O-glycanase treatment. The N-linked oligosaccharides seem to be of the complex type rather than the high-mannose or hybrid type and lack terminal sialic acid, as demonstrated by their resistance to endoglycosidases D and H and neuraminidase treatments. This sensitivity pattern was similar in both species, and the shift in the molecular size of the receptors to 35-38 kDa after PNGase F treatment occurred through one intermediate product, suggesting that both receptors contain a similar 35-38 kDa polypeptide core with two N-linked complex-type oligosaccharides, the heterogeneity of which is responsible for the species difference in receptor size. Papain treatment alone or followed by PNGase F produced in both species a 33-36 kDa membrane-bound fragment that was still able to bind the ligand, suggesting that the oligosaccharides are located on the approx. 2 kDa papain-cleavable polypeptide fragment of the receptors. The cleavage sites for both papain and PNGase F were hidden in occupied receptors, suggesting a conformational or topographical change in these upon ligand binding. Scatchard analyses and cross-linking experiments demonstrated that carbohydrates are not required for high-affinity ligand binding and that the 33-36 kDa membrane-bound papain fragment of both receptors contains the ligand-binding site.
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PMID:Rat and human neutrophil N-formyl-peptide chemotactic receptors. Species difference in the glycosylation of similar 35-38 kDa polypeptide cores. 185 49

C1q binds to and elicits cellular responses by several cell types, including monocytes, macrophages, neutrophils, B cells, and fibroblasts. The cell-binding domain is located within the collagen-like pepsin-resistant region of the C1q molecule (C1q tails). An affinity matrix of C1q tails coupled to Sepharose was used to select C1q-binding proteins from detergent extracts of surface-iodinated human monocytes, polymorphonuclear leukocytes, and the U937 cells. The major radiolabeled polypeptide eluted specifically from the ligand affinity column had an apparent molecular mass (Mr) of 126,000. Minor iodinated components eluted from Sepharose-tails migrated with Mr of 216,000 and 55,000. When subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions no change in the migration of any of these polypeptide bands was detected. None of these polypeptides reacted with antibodies directed against the integrins alpha 5 beta 1 (fibronectin receptor) or alpha v beta 3 (vitronectin receptor), LFA-1, or to several other cell adhesion molecules. The Mr 126,000 band was found to contain more than one polypeptide. Lectin binding properties, susceptibility to glycosidases and proteases, and immunoreactivity with the monoclonal antibody L-10, indicated that CD43 (sialophorin/leukosialin) is a component of this band. However, further data show that a monoclonal antibody, generated by immunization with the isolated Clq-binding fractions, recognizes a cell surface sialoglycoprotein distinct from CD43 and inhibits the C1q-mediated enhancement of phagocytosis in monocytes. These latter observations provide the first definitive connection between a specific phagocytic cell surface protein and a known C1q-mediated function. While these proteins contain sialic acid, binding assays and functional assays using neuraminidase-treated cells demonstrate that the functional interaction between C1q and the cell surface is not via sialic acid. The data taken together indicate either that the functional C1q receptor on phagocytic cells is a multi-subunit complex or that multiple proteins can interact with the fragment of C1q containing the cell-binding domain, at least one of which is involved in the C1q-mediated enhancement of phagocytosis.
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PMID:Phagocytic cell molecules that bind the collagen-like region of C1q. Involvement in the C1q-mediated enhancement of phagocytosis. 193 90

The role of the glycan moiety of the rat ovarian LH/CG receptor and human CG (hCG) in high-affinity receptor-hormone interaction was investigated by cross-linking and quantitative binding experiments. hCG and its derivatives, desialylated hCG and deglycosylated hCG were labeled either to the alpha-subunit (125I) or the beta-subunit (3H). The ligands were attached to ovarian membrane particles, which were treated with neuraminidase or peptide-N-glycosidase F to remove terminal sialic acids or N-linked oligosaccharides of the receptor, respectively, and the complexes formed were solubilized, cross-linked with glutaraldehyde, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All of the ligands produced similar autoradiographic patterns with the native or glycosidase-treated receptor, and only the receptor-(alpha)hCG and receptor-(alpha, beta)hCG complexes were detected. Moreover, quantitative binding studies indicated that all of the hormone derivatives had similar affinities for the native or glycosidase-treated receptor. In addition, the orientation of the carbohydrate side chains on the receptor-hormone complex was studied by digesting the complex with the glycosidases. The molecular weight of the receptor, evidenced by ligand blotting, was reduced to the same extent, whether the membrane-bound free receptor or receptor-hormone complex was treated with the glycosidases, suggesting that the oligosaccharide side chains of the receptor are apart from the hormone binding region. As peptide-N-glycosidase F treatment reduced the size of the Mr 90,000 receptor first to about Mr 67,000 and finally to about Mr 62,000, there may possibly be 2 N-linked carbohydrate chains per receptor polypeptide. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the glycosidase-treated receptor-[125I]hCG complex also revealed that neuraminidase was able to remove the sialic acids from both subunits of the receptor-bound hormone. In conclusion, the results suggest that hCG interacts with the polypeptide backbone of its ovarian receptor mainly through the peptide core of its alpha-subunit. Moreover, the carbohydrate side chains of both subunits of hCG are positioned on the outward face of the receptor-hormone complex.
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PMID:Significance of the glycan moiety of the rat ovarian luteinizing hormone/chorionic gonadotropin (CG) receptor and human CG for receptor-hormone interaction. 199 42

We isolated 7.4 mg of pure renin from 2 kg of rat kidneys using affinity chromatography on pepstatin-aminohexyl-Sepharose and an octapeptide renin inhibitor, H-77-Sepharose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that renin consists of two polypeptide chains linked by a disulfide bond, one of Mr = 36,000 (heavy chain) and the other of Mr = 3,000 (light chain). The amino-terminal 10-amino acid sequences of the heavy and the light chains were identical to the sequences beginning at Ser72 and Asp355, respectively, of the amino acid sequence of preprorenin deduced from the renin cDNA sequence. Amino acid sequencing of the carboxyl-terminal peptide of the heavy chain, generated by digestion with lysyl endopeptidase, showed that the carboxyl-terminal residue of the heavy chain is Phe. Thus, the propeptide of prorenin is cleaved after Thr71, followed by removal of two amino acids, Arg353 and Asn354, the result being formation of the heavy and light chains. Thus, the site of cleavage of rat prorenin is after a nonbasic amino acid, in contrast to the cleavage of the propeptide after a pair of basic amino acids in mouse submaxillary renin, human renal renin, and many secretory proteins. Treatment of renin with neuraminidase or glycopeptidase F had no apparent effect on the charge heterogeneity of renin. Glycosylation probably does not contribute to charge heterogeneity.
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PMID:Amino-terminal amino acid sequence and heterogeneity in glycosylation of rat renal renin. 201 14

We have proposed previously that the polysialic acid (PSA) moiety of NCAM can influence membrane-membrane apposition, and thereby serve as a selective regulator of a variety of contact-dependent cell interactions. In this study, cell and tissue culture models are used to obtain direct evidence that the presence of PSA on the surface membrane can affect both cell-cell and cell-substrate interactions. Using a neuroblastoma/sensory neuron cell hybrid, it was found that removal of PSA with a specific neuraminidase (endo-N) augments cell-cell aggregation mediated by the L1 cell adhesion molecule as well as cell attachment to a variety of tissue culture substrates. In studies of embryonic spinal cord axon bundling, which involves both cell-cell and cell-substrate interactions, the pronounced defasciculation produced by removal of PSA is most easily explained by an increase in cell-substrate interaction. The fact that in both studies NCAM's intrinsic adhesion function was found not to be an important variable further illustrates that regulation of the cell surface by PSA can extend beyond binding mediated by the NCAM polypeptide.
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PMID:NCAM polysialic acid can regulate both cell-cell and cell-substrate interactions. 205 Jul 39

1. Human, bovine and equine transferrins have been characterized with respect to mol. wt, and behavior on urea-polyacrylamide gels, and isoelectric focussing gels. 2. As shown by SDS-polyacrylamide gel electrophoresis human transferrin has one major polypeptide whereas both bovine and equine transferrins have two polypeptides. 3. The transferrins show multiple banded patterns on urea-polyacrylamide and isoelectric focussing gels, particularly when iron saturated. The various forms are not resolved by neuraminidase treatment.
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PMID:Electrophoretic characterization of human, equine and bovine transferrins. 206 Feb 80

The 90-kDa antigen, previously identified by the monoclonal antibody 1G7 to be a stage-specific surface protein of metacyclic trypomastigotes of Trypanosoma cruzi, has been further characterized in this study. Experiments of metabolic labeling with [35S]methionine, [2H]mannose and [3H]galactose revealed that the 90-kDa antigen is the main glycoprotein synthesized by metacyclic forms (G strain). Through pulse-chase experiments with [35S]methionine-labeled metacyclic trypomastigotes, it was found that the antigen is synthesized as a 75-kDa precursor polypeptide that is rapidly processed to the mature 90-kDa molecule. When metacyclic trypomastigotes were treated with tunicamycin, the production of 90-kDa antigen was greatly diminished, and the 75-kDa species, which was also expressed on the cell surface, accumulated. Concanavalin A bound strongly to the 90-kDa antigen, but failed to recognize the 75-kDa polypeptide. Treatment of neuraminidase had no effect on the 90-kDa antigen, whereas digestion by endoglycosidase H generated a polypeptide of 82 kDa. Altogether these data indicate that the 90-kDa antigen is a glycoprotein containing N-linked oligosaccharide side chains of the high-mannose type. The 90-kDa glycoprotein may be involved in the process of host cell invasion, since the internalization of metacyclic forms into Vero cells was partially inhibited by monoclonal antibody 1G7.
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PMID:The stage-specific 90-kilodalton surface antigen of metacyclic trypomastigotes of Trypanosoma cruzi. 210 76

We report here the study of the glycosylation pattern of human recombinant (r) IL2 expressed in a Chinese hamster ovary (CHO) cell line. The human rIL2 secreted by this high-producing recombinant CHO cell line was metabolically radiolabelled with [35S]-methionine, or with [3H]-glucosamine and [3H]-galactose, purified to homogeneity, and then characterized. The electrophoretic analysis of the [35S]-methionine-labelled proteins present in the culture medium of the CHO cell line showed that the rIL2 represents approximately 12% of the total secreted proteins. Furthermore, pulse-chase experiments showed that the glycosylated rIL2 is synthesized and secreted within 30 min. The point of attachment and the structure of the carbohydrate moiety of the rIL2 was determined by: amino-terminal sequencing and fingerprint analysis of the 3H-labelled rIL2, mass spectroscopy of the amino-terminal tryptic octapeptide, and carbohydrate analysis after enzymatic (Vibrio cholerae neuraminidase and Aspergillus oryzae beta-galactosidase) or sulfuric acid hydrolysis. The results indicate that the recombinant protein possesses a sugar moiety O-linked to the threonine residue at position 3 of the polypeptide chain, and that sialic acid, galactose and N-acetyl galactosamine are components of this carbohydrate moiety. Taken together these results suggest that the recombinant molecule is identical to natural IL2.
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PMID:Closely related glycosylation patterns of recombinant human IL-2 expressed in a CHO cell line and natural IL-2. 210 57

Lysosomal neuraminidase (sialidase; EC 3.2.1.18) and beta-galactosidase (EC 3.2.1.23), together with a carboxypeptidase, the so-called 'protective protein', were co-purified from the human placenta by affinity chromatography on a concanavalin A-Sepharose column followed by a thiogalactoside-agarose affinity column for beta-galactosidase. Analysis of the purified material by gel-filtration h.p.l.c. revealed three distinct molecular forms, all with high beta-galactosidase specific activity, but only the largest one expressed neuraminidase activity. Rechromatography of each individual species separately indicated that all three are in fact part of an equilibrium system (the neuraminidase-beta-galactosidase-carboxypeptidase complex or NGC-complex) and that these species undergo slow conversion into one another through dissociation and association of protomeric components. Each species was sufficiently stable for the determination of their hydrodynamic properties by gel-filtration h.p.l.c. and sedimentation velocity. The largest species had an apparent sedimentation coefficient S20.w, of 18.8 S and a Stokes' radius of 8.5 nm, giving a molecular mass of 679 kDa and a fractional ratio, f/f min, of 1.47. The latter value indicates that the macromolecule is asymmetric or highly hydrated. This large species is composed of four types of polypeptide chains of molecular mass 66 kDa (neuraminidase), 63 kDa (beta-galactosidase), 32 kDa and 20 kDa (carboxypeptidase heterodimer). The 32 kDa and 20 kDa protomers are linked together by a disulphide bridge. Glycopeptidase F digestion of the NGC-complex transformed the diffuse 66-63 kDa band on the SDS gel into two close but sharp bands at 58 and 56 kDa. The two smaller species which were separated on the h.p.l.c. column correspond to tetrameric and dimeric forms of the 66-63 kDa protomers and express exclusively beta-galactosidase activity. Treatment of the NGC-complex with increasing concentrations of guanidinium hydrochloride up to 1.5 M also resulted in dissociation of the complex into the same smaller species mentioned above plus two protomers of molecular mass around 60 and 50 kDa. A model of the largest molecular species as a hexamer of the 66-63 kDa protomers associated to five carboxypeptidase heterodimers (32 kDa and 20 kDa) is proposed
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PMID:Structure of the lysosomal neuraminidase-beta-galactosidase-carboxypeptidase multienzymic complex. 210 3

ASA-NeuAc2en, a photoreactive arylazide derivative of sialic acid, is shown to be a powerful competitive inhibitor of lysosomal neuraminidase from bovine testis (Ki approximately 21 microM). Photoaffinity labeling and partial purification of preparations containing this lysosomal neuraminidase activity result in specifically and non-specifically labeled polypeptides. Only labeling in a 55 kDa polypeptide is found to be specific, since it could be prevented by the competitive neuraminidase inhibitor NeuAc2en. We conclude that the 55 kDa polypeptide in the bovine testis beta-galactosidase/neuraminidase/protective protein complex contains the catalytic site of neuraminidase.
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PMID:Photoaffinity labeling of the lysosomal neuraminidase from bovine testis. 212 79


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