Biosynthesis of Procollagen [ ( proal V ) , ( proa 2 V ) ] by Chick Tendon Fibroblasts and Procollagen ( proal V ) , by Hamster Lung Cell Cultures

Chick embryo tendon fibroblasts were cultured with [3H]amino acids for 4, 8, and 24 h. Procollagen V was found in the cell layer. The chain composition predominantly corresponded to [(proal V), prorv2 VI, and a small proportion existed as the disulfide-linked heterotrimer and dimer. It was progressively converted to p-collagen V and collagen V which were found both in the cell layer and in the culture medium. Processing proceeded as previously described for chick tissues including the attachment of a noncollagenous peptideP to the pa2 V chain. The smallest chains were also larger than a V(pepsin). Cultures of Chinese hamster lung cells (clone HT1) synthesized the homotrimer (proal V)s. This lacked intermolecular disulfide bridges, was not processed, and remained associated with the cell layer. The chick fibroblast-conditioned culture media contained an enzymatic activity which converted procollagen V of blood vessels to p-collagen V. This p-collagen V lacked the noncollagenous peptide-P which is normally found associated by disulfide linkage to the pa2 V chain. This enzymatic activity also converted the hamster cell (proal V), to p-collagen V. Arginine inhibited this processing step. We conclude that the processing of procollagen V occurs extracellularly, is defective in the hamster lung cell cultures and that the type V molecules remain largely associated with the cell layer. The previously proposed parallel biosynthesis of homoand heteroprocollagens V, and their subsequent processing in tissues are consistent with the present results.