Assembly and processing of procollagen V (AB) in chick blood vessels and other tissues

The biosynthesis and processing of type V procollagens was investigated in chick embryo blood vessels labeled with radioactive amino acids. Monomeric, pepsin-sensitive pro alpha 1 V and pro alpha 2 V chains are slowly assembled into triple helically folded molecules. A small proportion of these procollagen V molecules contain interchain disulfide bridges, and the disulfide-linked heterodimer and heterotrimer (pro alpha 1 V)2pro alpha 2 V were found. A relatively fast conversion of procollagen V to p-collagen V is followed by slow change to collagen V. This time course is similar to the processing of procollagen III and is much slower than the rate of appearance of type I collagen in blood vessels. A combination of sedimentation and electrophoretic analyses was used to measure the relative size of the type V chains and to demonstrate attachment of noncollagenous peptides (Mr = 33,000) to p alpha 2 V by disulfide linkage. Similar quantitative pulse-chase studies were made with calvaria and crop. As the same unusual features of assembly and processing of type V chains were seen in muscle, bone, and blood vessels, we conclude that these are characteristic of type V collagen biosynthesis.