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The covalent structure of collagen. Amino-acid sequence of peptide 1-CB6-C2.

Sequencing of chymotrypsin, trypsin, collagenase- and hydroxylamine-derived peptides, using the automated Edman degradation procedure, yielded the complete amino acid sequence of α2-CB4 from calf skin collagen (321 residues). Together with the data from earlier work, an uninterrupted sequence in the helical region of the α2-chain from residues 1–393 is now known. Glycine is found in every third position of the peptide. Hydroxylation of proline and lysine occurs only in the Y-position of the triplet Gly-X-Y and is not complete in every position. Some residues, such as glutamic acid, leucine, phenylalanine and arginine, are distributed non-randomly between the X and Y-positions and this non-random distribution is different in the α1 and α2-chains. Comparison of the N-terminal 393 residues from the helical region of the α1 and α2-chains revealed a nearly identical distribution of charged polar residues arginine, lysine, glutamic and aspartic acids. The distribution of the triplet Gly-Pro-Hyp is similar in both chains. The remaining residues in the α2-chain exhibit a high degree of substitutions when compared with those in the α1-chain. Approximately one in every two residues in both the X and Y-positions are substituted.