Post-translational modifications occur in the rER and Golgi. The signal peptide is cleaved. Lysine and proline residues are hydroxylated. Hydroxylysine residues are glycosylated. N-linked sugars are added to the terminal portion of the polypeptide.
Polypeptide chains form a triple helix molecule.
Procollagen is formed through intrachain and interchain disulfide bonds which stabilise the polypeptides and determine the shape of the molecule. Procollagen is packed into secretory granules which move along microtubules to be released into the extracellular matrix Extracellular Events Uncoiled terminal ends of procollagen are cleaved to form tropocollagen. Fibrils aggregate to form collagen fibres. Collagen catabolism is poorly understood, but enzymatic processes and mechanical factors may be involved. The process of proteoglycan synthesis begins with translation of mRNA to form a protein core to which glycosaminoglycan chains are added.