Segment-long-spacing aggregates and isolation of COOH-terminal peptides from type I procollagen.

Abstract
Type I procollagen secreted by matrix-free cells from chick embryo tendons was purified by DEAE-cellulose chromatography. EM of segment-long-spacing aggregates of the procollagen demonstrated the presence of both NH2-terminal and COOH-terminal extensions not found in collagen. The procollagen was digested with bacterial collagenase and the COOH-terminal fragments were isolated by gel filtration and polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Analysis of tryptic peptides demonstrated that the COOH-terminal extensions on the pro.alpha.1 and pro.alpha.2 chains had different primary structures.