Biosynthesis of A,B procollagen.

Interest in cell-associated collagens led others to isolate A and B collagen chains, also known as type V collagen, from many tissues, but only after pepsin cleavage. Soluble precursors of these chains are synthesized in vitro by crop, a chicken embryo muscle tissue, and are converted by at least two processing steps from procollagens via intermediates to final forms which are large than the pepsin-derived A and B chains. Heterotrimeric, disulfide-bridged procollagen molecules corresponding to B2A exist. Components were separated by ion exchange chromatography, velocity sedimentation, and electrophoresis, and the relationships between them were established by sequential radioactive labeling and comparison of peptides generated by protease cleavage.