ANTERIOR LENS CAPSULE COLLAGENS - CYANOGEN-BROMIDE PEPTIDES OF THE C CHAIN

Collagen was extracted from bovine anterior lens capsule by limited proteolysis with pepsin for 40 h at 4 °C. After purification, the collagen preparation was denatured and fractionated by gel filtration and carboxymethylcellulose chromatography. Three polypeptide chains of approximately α-chain size designated C, C-1, and D are described. The apparent molecular weight estimated by gel filtration of the C and D chains is 95 000, while that of the C-1 chain is 110000. However, the apparent molecular weight estimated by sodium dodecyl sulfate gel electrophoresis of C is 95 000, of D 75 000, and of C-1 140000. The C and C-1 chains were cleaved with CNBr, and the resulting peptides were separated, purified, and characterized with respect to amino acid composition and apparent molecular weight. A total of 12 CNBr peptides was obtained from the digest of the C chain, which together accounted for the amino acid content of the intact chain. The CNBr cleavage of the C-1 chain yielded a total of 13 peptides, 12 of which were identical with those obtained from the C chain in amino acid composition and chromatographic properties. The one extra peptide, CB13, contained 183 residues of amino acid. These 13 peptides together account for the amino acid content of the C-1 chain. From these data, we conclude that the C and C-1 chains are derived from the same molecule and that the observed difference in the molecular weight might be attributable to different sites of scission by pepsin. The amino acid composition of the D chain differs significantly from that of the C or C-1 chain. Furthermore, the sodium dodecyl sulfate gel electrophoretic pattern of the CNBr digest of the D chain is substantially different from that of C or C-1. From these observations, we conclude that, contrary to earlier suggestions, bovine anterior lens capsule contains at least two separate collagen chains, C (or C-1) and D. Evidence is insufficient to decide whether the C and D chains are from the same or different molecules. © 1979, American Chemical Society. All rights reserved.