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Biomedical subjects

P Bornstein

Publications and source records attributed to P Bornstein.

At least 199 records · Page 11Linked to original sources
PubMed1971

The distribution of antigenic determinants in rat skin collagen.

Immunological studies of rat skin collagen were carried out with a sensitive and quantitative radioimmunoassay. Hyperimmune rabbit antisera to rat skin collagen and isolated alpha2 chains were used. Iodine-labeled alpha chains and CNBr-produced peptides served as test antigens, and native collagen, alpha chains, and CNBr peptides were employed as inhibitors in the assay. The alpha1 and alpha2 chains were immunologically distinct. Although the alpha1 chain was not immunogenic, antibodies to alpha1 were detected in antisera to the intact collagen molecule. The major antigenic determinant of the alpha1 chain was located in alpha1-CB6 which constitutes the carboxy-terminal region of the chain. The alpha2 chain contained two non-cross-reacting antigenic determinants, one in the amino-terminal region (alpha2-CB1) and the other in the carboxy-terminal region (alpha2-CB5) of the chain. The native collagen molecule was less effective than isolated alpha chains in inhibiting binding of labeled peptides to antisera, indicating that antigenic determinants were less accessible in the triple helical molecule. These immunologic studies are consistent with preliminary comparative biochemical data which indicate that interspecies structural differences in collagen predominate at both the amino- and carboxy-terminal ends of the chains.

Animals↗
PubMed1971

Evidence for procollagen, a biosynthetic precursors of collagen.

Incubation of rat calvaria for short times in the presence of a labeled amino acid revealed the existence of a collagen fraction (procollagen) that functions as a biosynthetic precursor of collagen. Procollagen contains an alpha1-like chain (pre-alpha1) that elutes earlier from CM-cellulose than does rat-bone alpha1 and has a molecular weight, estimated by acrylamide gel electrophoresis, of 120,000. A time-dependent conversion of pre-alpha1 to alpha1 was demonstrated by incubation of calvaria for periods varying from 9 to 60 min and by a pulse-chase experiment. Limited cleavage of procollagen with pepsin resulted in a molecule with a chain resembling alpha1 in chromatographic properties, molecular weight, and relative hydroxyproline and proline contents. Thus, conversion of procollagen to collagen is likely to occur in vivo by a proteolytic mechanism. The additional peptide sequences in procollagen may serve to initiate chain association in triple-helix formation, to facilitate molecular transport, and to inhibit intracellular fibrogenesis.

Animals↗
PubMed1969

The elastic fiber. I. The separation and partial characterization of its macromolecular components.

The two morphologically different constituents of the mature elastic fiber, the central amorphous and the peripheral microfibrillar components, have been separated and partially characterized. A pure preparation of elastic fibers was obtained from fetal bovine ligamentum nuchae by extraction of the homogenized ligament with 5 M guanidine followed by digestion with collagenase. The resultant preparation consisted of elastic fibers which were morphologically identical with those seen in vivo. The microfibrillar components of these elastic fibers were removed either by proteolytic enzymes or by reduction of disulfide bonds with dithioerythritol in 5 M guanidine. The microfibrils solubilized by both methods were rich in polar, hydroxy, and sulfur-containing amino acids and contained less glycine, valine, and proline than the amorphous component of the elastic fiber. In contrast, the amino acid composition of the amorphous component was identical with that previously described for elastin. This component demonstrated selective susceptibility to elastase digestion, but was relatively resistant to the action of other proteolytic enzymes and to reduction. These observations establish that the microfibrils consist of a different connective tissue protein (or proteins) that is neither collagen nor elastin. During embryologic development the microfibrils form an aggregate structure before the amorphous component is secreted. These microfibrils may therefore play a primary role in the morphogenesis of the elastic fiber.

Amino Acids↗