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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pepsin-solubilized bovine corium collagen was purified, reconstituted, and treated with various levels of glutaraldehyde. Treatment of suspensions of fibrillar collagen with low concentrations of glutaraldehyde appeared to have little effect on the gross morphology of fibrils, as judged by electron microscopy, but did have a significant impact on their physicochemical stability. Fibrillar collagen treated with glutaraldehyde at a concentration equal to or greater than 0.0075% demonstrated significant decreases in neutral solubility at elevated temperatures as compared to noncross-linked controls. Differential scanning calorimetry provided a convenient and quantitative means to correlate increases in melting temperature with increases in glutaraldehyde treatment concentration. Fibrillar collagen cross-linked with glutaraldehyde concentrations as low as 0.0075% demonstrated a significantly greater resistance to proteolytic degradation than did noncross-linked fibrillar collagen samples. The residual, extractable aldehyde content of such preparations was between 1 and 3 ppm. Rheological measurements on such cross-linked suspensions demonstrated that they were non-Newtonian, shear-thinning fluids, and that they were two- to threefold more viscous than corresponding preparations of noncross-linked collagen.
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PMID:The preparation and physicochemical characterization of an injectable form of reconstituted, glutaraldehyde cross-linked, bovine corium collagen. 351 69

We have studied the effects of 2,3-diphosphoglycerate (2,3-DPG), 3-phosphoglycerate (3-PG), 3-phosphoglyceraldehyde (3-PGA), 2-phosphoglycerate (2-PG) and beta-glycerol phosphate (beta-GP) on platelet aggregation and on thromboxane B2 (TXB2) formation. The results show that 2,3-DPG, 3-PG, and 3-PGA inhibited platelet aggregation and TXB2 formation induced by norepinephrine, ADP, epinephrine, and collagen; but they also induced platelet aggregation and TXB2 formation in the presence of subthreshold concentrations of Na arachidonate. 2-PG and beta-GP were inactive. The results also show that there is a structure-function relationship between 2,3-DPG, 3-PG, and 3-PGA with platelet aggregation phenomena and prostaglandin synthesis.
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PMID:Structure-function relationship of 3-phosphoglycerate analogues with platelet aggregation and thromboxane A2 formation. 359 60

Pepsin-solubilized collagen VI was prepared from human placenta and used to separate three constituent chains for determining partial amino acid sequences. Antibodies raised against the chains assisted in the identification and purification of several cDNA clones from three expression lambda gt11 libraries. Most of the clones hybridized to either a 3.5-kb or 4.2-kb mRNA species which by matching peptide and nucleotide sequences could be identified as coding for the alpha 2(VI) or alpha 1(VI) chain, respectively. Other clones hybridized to either an 8.5-kb mRNA which very likely encoded the alpha 3(VI) chain or to an unknown 2.0-kb mRNA. Northern blots revealed a considerable variation in the mRNA levels for each collagen VI chain in both skin and cornea fibroblasts and in several tumor cell lines. Limited sequence data generated from peptides and cDNA clones demonstrated a characteristic cysteine pattern at the junction between N-terminal globular domain and triple helix in all three chains. In addition, the data showed occasional interruptions of triplet sequences within the triple-helical domain and the presence of two Arg-Gly-Asp sequences which are potential cell-binding structures.
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PMID:Characterization of three constituent chains of collagen type VI by peptide sequences and cDNA clones. 366 27

The effect of pepsin solubilization on the platelet aggregating activity of type I collagen and type III collagen was examined. Pepsin-digested type I collagen was unable to initiate platelet aggregation in either soluble form or as pre-formed fibrils. In contrast, pepsin-digested type III collagen was active in soluble form or as preformed fibrils. Mixtures of type I and type III collagen were assayed for platelet aggregating activity. In soluble form, these mixtures demonstrated elevated activity with increasing type III concentration. When the mixtures were tested as pre-formed fibrils, the rate of aggregation was relatively constant with the combination 75% type III and 25% type I manifesting the highest activity. The lag time for onset of aggregation was also minimized for this same type III/type I ratio. The combinations of the two collagen types formed fibrils which reflected the amounts of types I and III collagens in solution.
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PMID:The effect of pepsin solubilization on platelet aggregation by types I and III collagens. 392 48

Pepsin-solubilized bovine corium collagen was reconstituted by rapid neutralization in dilute phosphate buffer at temperatures ranging from 10 degrees C-25 degrees C. The resultant fibrils were harvested by centrifugation and resuspended in physiological buffer to a constant protein concentration. The optical density of such suspensions, measured at 410 nm in a 1 mm path length cuvette, exhibited a strong inverse correlation with temperature of fibrillogenesis. The absorbance values of fibrillar suspensions prepared from intact collagen were greater than those observed with suspensions prepared from pepsin-solubilized collagen under similar conditions and demonstrated a reduced dependence on temperature of fibril assembly. The nature of the variation in opacity of fibrillar suspensions prepared from pepsin-solubilized material was further investigated using transmission electron microscopy, trypsin sensitivity, SDS gel electrophoresis and polarimetry. Reconstitution conditions that favored more rapid precipitation (e.g., higher incubation temperatures) tended to produce fibril suspensions of lower opacity (translucent). These translucent suspensions exhibited fibrils that were small in diameter when compared to fibril suspensions of higher opacity. Translucent preparations also contained higher levels of a trypsin sensitive, early melting component and displayed a higher proportion of peptides migrating faster than alpha 2(I) on SDS polyacrylamide gels. Collagen preparations depleted of the early melting component continued to demonstrate the correlation between increased temperature and decreased fibrillar opacity, suggesting that the two phenomena were independent. It is proposed that the unstable components are nicked or shortened collagen helices, presumably generated by pepsinization or the action of endogenous proteases of the bovine corium, which are differentially incorporated into fibrils depending on the conditions of fibril assembly.
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PMID:Collagen fibrillogenesis in vitro: a characterization of fibril quality as a function of assembly conditions. 392 70

Quantification and biosynthesis of type I and type III collagens were determined in skin of control and Fraser mice (CatFraser mutation), which exhibit a genetically determined cataract. Skin organ cultures were labelled with [3H]proline. Pepsin-solubilized collagens were studied using three different approaches: (a) differential salt precipitation at neutral pH, followed by SDS-polyacrylamide gel electrophoresis; (b) differential salt precipitation at acid pH followed by SDS-polyacrylamide gel electrophoresis. (c) CNBr peptide analysis. These methods gave consistent and reproducible results, indicating a selective decrease of type I collagen in Fraser mouse skin as compared to control mouse skin. Metabolic labelling of skin organ cultures showed a decreased specific radioactivity of hydroxy[3H]proline in type I collagen of Fraser mouse skin. The concordant results of these experiments suggest a genetically determined alteration of interstitial collagen metabolism in the Fraser mutation apparently specifically concerning the expression of type I collagen gene(s).
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PMID:Selective decrease of type I collagen synthesis in Fraser mice skin. 393 69

Both the triple-helical and denatured forms of nonfibrillar bovine dermal type I collagen were tested as substrates for the catalytic subunit of cAMP-dependent protein kinase in an in vitro reaction. Native, triple-helical collagen was not phosphorylated, but collagen that had been thermally denatured into individual alpha chains was a substrate for the protein kinase. Catalytic subunit of cAMP-dependent protein kinase phosphorylated denatured collagen to between 3 to 4 mol of phosphate/mol of (alpha 1(I)2 alpha 2(I). Pepsin-solubilized and intact collagens were phosphorylated similarly, as long as each was in a nonhelical conformation. The first 2 mol of phosphate incorporated into type I collagen by the protein kinase were present in the alpha 2(I) chain. The alpha 1(I) chain was only phosphorylated during long incubations in which the stoichiometry exceeded 2 mol of phosphate/mol of (alpha 1(I)2 alpha 2(I). Phosphoserine was the only phosphoamino acid identified in collagen that had been phosphorylated to any degree by the protein kinase. The 2 mol of phosphate incorporated into the alpha 2(I) chain were localized to the alpha 2(I)CB4 cyanogen bromide fragment. The catalytic subunit of cAMP-dependent protein kinase phosphorylated denatured pepsin-solubilized collagen with a Km of 8 microM and a Vmax of approximately 0.1 mumol/min/mg of enzyme. Denatured, but not triple-helical, type I collagen was also phosphorylated by cGMP-dependent protein kinase, although it was a poorer substrate for this enzyme than for the cAMP-dependent protein kinase. Collagen was not a substrate for phospholipid-sensitive Ca2+-dependent protein kinase. These results suggest the potential for nascent alpha chains of type I collagen to be susceptible to phosphorylation by cAMP-dependent protein kinase in vivo prior to triple-helix formation. Such a phosphorylation of collagen could be relevant to the action of cAMP to increase the intracellular degradation of newly synthesized collagen.
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PMID:In vitro phosphorylation of type I collagen by cyclic AMP-dependent protein kinase. 395 36

A procollagen in the soluble fraction of rabbit vitreous was isolated by dialysis against dilute acetic acid and partially purified by Bio-Gel A 5M gel filtration. The molecule was identified to be type II procollagen by comparing its segment-long-spacing (SLS) banding pattern with that of standard type II collagen isolated from rabbit articular cartilage. Electron microscopy of the SLS of this type II procollagen revealed a fuzzy propeptide extension at the N-terminal end of the molecule. Pepsin digestion of the procollagen removed this extension, thus converting the molecule into a collagen which had mobility similar to that of pepsin-soluble cartilage type II collagen in SDS-polyacrylamide gel electrophoresis. No inter-chain disulfide bond was found in the propeptide extension when the procollagen samples were electrophoresized with or without mercaptoethanol. Comparison of the cyanogen bromide peptide map of the type II procollagen with that of the pepsin-soluble type II collagen indicated that two extra peptides were present in the digest of procollagen. All of this evidence suggested that the procollagen in the soluble vitreous body of the rabbit eye was a novel type II procollagen with a propeptide extension only at the N-terminus.
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PMID:Identification of type II procollagen in rabbit vitreous. 401 Nov 29

1. Collagen was extracted from chick skin with dilute acetic acid followed by dilute acetic acid containing pepsin. 2. The solubilized collagens were purified and portions subjected to further digestion by pepsin. 3. This treatment decreased the aldehyde content but contamination by hexosamine was not diminished. 4. Pepsin treatment converted practically all the acid-soluble collagen into monomeric subunits (alpha-chains), but the pepsinsolubilized material retained a significant amount of higher subunits (beta- and gamma-chains). 5. Treatment lowered the rate of fibrillogenesis by acid-soluble collagen, but was without effect on pepsin-solubilized collagen.
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PMID:Pepsin treatment of avian skin collagen. Effects on solubility, subunit composition and aggregation properties. 457 95

Components were solubilized from human glomerular basement membrane by digestion with collagenase and pepsin or by extraction with guanidine-HCl either directly or after previous digestion with the enzyme. The diverse preparations were used as antigens in the enzyme-linked immunosorbent assay (ELISA) of antibody titers in sera from patients with Goodpasture syndrome and patients with other forms of glomerulonephritis, that is, systemic lupus erythematosus, periarteritis nodosa, and IgA-related nephropathy. Patients with Goodpasture syndrome had high titers of IgG antibodies reacting most strongly with collagenase digests. The antigen(s) was only partly solubilized by guanidine-HCl extraction, was destroyed by pepsin digestion as well as reduction, and partly destroyed by trypsin digestion. The antigen(s) is most likely noncollagenous protein. Antibodies from patients with other forms of nephritis were directed primarily against antigens in guanidine-HCl extracts, while the antigen(s) was not solubilized by collagenase digestion. Pepsin digestion destroyed the antigen(s). The antibodies were of a different class, that is, the patients with systemic lupus erythematosus had IgG and IgA as well as IgM antibodies; the patients with periarteritis nodosa had IgM or IgG and IgA antibodies, while the patients with IgA-related nephritis had the highest recorded titers of IgA but also had IgG as well as IgM antibodies. None of the patients had antibodies directed against triple helical collagen. The antibody response in anti-GBM antibody-related nephritis, then, is different both with respect to antigen and antibody class and depends on the underlying disease syndrome.
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PMID:Antiglomerular basement membrane antibody: antibody specificity in different forms of glomerulonephritis. 613 25


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