Lag between incorporation of proline into protocollagen and synthesis of hydroxyproline during collagen biosynthesis in vitro and in vivo.

Abstract

THE hydroxyproline and hydroxylysine in collagen are synthesized by hydroxylation of proline and lysine after these amino-acids have been incorporated into peptide linkages (for review see ref. 1). Experiments with embryonic cartilage in vitro in which the hydroxylases were intermittently inhibited demonstrated that the hydroxylations can occur after the proline-rich and lysine-rich polypeptide precursor protocollagen is released from ribosomal complexes1,2. There has been controversy, however, over the question of whether in uninhibited systems the hydroxylation of the appropriate prolyl and lysyl residues occurs while nascent polypeptide chains are still being assembled on ribosomes1,3,4.