In: Anatomy and Physiology
Outline the key cellular steps involved in the production of human type I collagen.
ANSWER: INSIDE THE CELL: Two types of alphachains- alpha 1 and alpha 2 are formed during translation on ribosome alon the rough endoplasmic reticulum. These peptide chains are called as preprocollagen.
These polypeptide chains are released into the lumen of rough endoplasmic reticulum.
Single peptides are cleaved inside the RER and the chains are known as proalpha chains.
Hydroxylation of prolin and lysine happens inside the lumen. It is ascorbic acid dependent process.
Glycolysation of specific hydroxylysine occurs. Triple alpha helix structure is formed in the endoplasmic reticulum from two alpha 1 chain and one alpha 2 chains. The formed procollagen is transported to the golgi complex where it is secreted by exocytosis.
OUTSIDE THE CELL:
Registration peptides are cleaved and tropocollagen is formed by procollagen peptidase.
Mulitple tropocollagen molecules from collagen fibrils via covalent cross linking by lysyl oxidase. Multiple collagen fibrils forms into collagen fibres. The formed collagen may be attached to cells membrane via several type of protein like integrin, fibronectin, laminin.