Isolation and Structure of the Amino-Terminal Cross-linking Region in Insoluble Type III Collagen

Abstract

A collagenous peptide T1X was isolated from a tryptic digest of the insoluble matrix of calf skin. The peptide consists of 2 identical polypeptide chains each with a length of 72 amino acid residues joined by a cross-link. Absorption spectra obtained from hydrazone and azine derivatives of T1X indicated that the peptide contains an aldol-type of cross-link (X). The sequence of 23 amino acid residues in the amino-terminal region was determined as Glx-Tyr-Glu-Ala-Tyr-Asp-Val-X-Ser-Gly-Val-Ala-Gly-Gly-Gly-Ile-Ala-Gly-Tyr-Hyp-Gly-Pro-Ala. This sequence overlaps the previously described amino-terminal sequence of .alpha.1 (III) chain obtained from pepsin treated, insoluble type III collagen. The present data demonstrate a nonhelical segment of 14 amino acid residues in type III collagen important for cross-linking.