The order of cyanogen-bromide peptides and location of carbohydrate in the alpha2 chain of guinea-pig skin collagen.

The alpha2 chain of guinea pig skin collagen contains two additional methionyl residues in comparison with the alpha2 chain of other vertebrate species. The order of the three CNBr peptides unique to the alpha2 chain was established on the basis of the homology of their primary structures to sequences of previously ordered regions in the alpha1 and alpha2 chains of other colagens. The two larger peptides, 4A + 4B, were found to correspond to the region homologous to alpha2-CB4 of other species, while the smaller peptide, 3A, was homologous to the NH2-terminal portion of alpha2-CB3. Thus, the order of the peptides in the alpha2 chain of this collagen is 1-O-4A-4B-2-3A-3B-5. Periodate oxidation and alkaline or acid hydrolysis of the CNBr fragments showed that all of the hydroxlysine-linked carbohydrate in the alpha2 chain was present in alpha2-CB4B. Carbohydrate analyses were most consistent with the existence of single monosaccharide and disaccharide units in this region.