Characterization of a large fragment from annelid cuticle collagen and its relationship to the intact molecule

Digestion of the cuticle collagen from the annelid Nereis virens with Clostridium histolyticum collagenase yields a native, collagenase-resistant fragment (CCRF) of the molecule with an Mr of about 900,000 (Kimura and Tanzer, J. Biol. Chem. 252: 8018, 1977). We have produced 940 nm long, SLS-crystallites from the collagenase-resistant fragment; the SLS pattern matches a region at one end of the 2,400 nm SLS obtained from intact cuticle collagen. Upon denaturation, the fragment yields two subunits, CCRFA and CCRFB, which can be separated by SDS polyacrylamide gel electrophoresis or by chromatography on DEAE-cellulose; the subunits are in about a 2:1 ratio. The subunits have amino acid compositions which are similar to those of the original A and B chains, although the fragments have a higher content of acidic residues and a lower content of hydroxyl residues. Previous studies of the intact B chain have shown that there is about one methionine in the chain, and that it is located near the COOH terminus. The CCRFB subunit also contains about one methionine, indicating that CCRFB is probably derived from the COOH end of the intact molecule. Based on these composite data, we have provisionally defined the amino and carboxyl ends of the cuticle collagen SLS and provide additional evidence that the molecule is a heteropolymer with the formula A(B)2.