Characterization of protease-resistant fragments of laminin mediating attachment and spreading of rat hepatocytes.

In attempts to identify cell binding domains in the basement membrane protein laminin (Mr = 900,000), responsible for the substrate attachment mediating activity of the protein, proteolytic fragments were isolated and compared with respect to their biological activity. The fragments analyzed were generated by digestion of the protein with elastase or pepsin and included the previously described fragments 1 to 4 and three additional fragments, 5, 6, and 7 with molecular weights of 30,000 to 50,000. Fragments 1, 5, and 6 promoted substrate attachment of rat hepatocytes.

Structural diversity and domain composition of a unique collagenous fragment (intima collagen) obtained from human placenta.

Intima collagen was obtained from pepsin digests of human placenta in two forms, which differ to some extent in the size of their constituent polypeptide chains (Mr 50 000-70 000). These chains are connected by disulphide bonds to large aggregates. The aggregates are arranged in a triple-helical conformation with a remarkably high thermal stability (Tm 41-62 degrees C) and are resistant to further proteolytic digestion.

A network model for the organization of type IV collagen molecules in basement membranes.

Type IV collagen was solubilized from a tumor basement membrane either by acid extraction or by limited digestion with pepsin. The two forms were similar in composition and the size of the constituent chains but differed when examined by electron microscopy and in the fragment pattern produced by bacterial collagenase. The acid-soluble form showed after rotary shadowing strands mainly of a length of 320 nm which terminated in a globule, or two strands connected by a similar globule.

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.

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.

Disulfide-linked cyanogen bromide peptides of bovine fibrinogen. II. Isolation and sequence analysis of the chain constituents from the amino terminal region.

Bovine fibrinogen was cleaved with CNBr and the peptide F-CB1 which originates from the amino end of the molecule was purified by chromatographic methods. After reduction and alkylation of F-CB1 three main polypeptide chains could be identified. They were derived from the A alpha chain (F-CB1 alpha), Bbeta chain (F-CB1 beta) and gamma chain (F-CB1 gamma) of fibrinogen and consisted of 54, 143 and 78 amino acid residues, respectively.