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Chymotryptic cleavage of α1-CB6, the C-terminal CNBr peptide of the α1-chain from calf skin collagen, yields three peptides, designated C1 (positions 1-113), C2 (positions 114-196) and C3 (positions 197-217), respectively. The present paper describes the amino acid sequence of C2. It was determined exclusively by application of the automated Edman degradation. The entire peptide C2 as well as some of its tryptic and thermolytic peptides were subjected to this procedure. The helical portion of α1-CB6-C2 (positions 114-192) was found to consist of tripeptide units containing glycine in every third position, hence being typical of the collagen structure. The α1-chain of calf skin collagen contains a 3-hydroxyproline residue which was located in position 164 in the tripeptide unit Gly-3Hyp-4Hyp. This is the first case of a vertebrate collagen in which hydroxylation was found of a proline in position X of the tripeptide unit Gly-X-Y. The helical part of the α1-chain terminates in a five-fold repetition of the tripeptide Gly-Pro-Pro. The four C-terminal amino acids of C2 are already part of the nonhelical area at the end of the α1-chain which in addition comprises the entire peptide C3. [ABSTRACT FROM AUTHOR]