Your friend, who is an engineering major, is interested in the mechanical proper

Question

Your friend, who is an engineering major, is interested in the mechanical properties of extracellular matrix and wants to study how secreted collagen molecules assemble into a collagen fiber. As part of his studies, he has been trying to speed up the rate at which cells can produce the collagen protein and is considering reducing the size of the propeptide that is attached to the collagen chain such that it contains only the ER targeting sequence as well as the site for cleavage of the propeptide. To his surprise, this modification causes collagen to be degraded inside the cell. Can you explain why

Explanation / Answer

Extracellular matrix secrete fibrous protein, collagen that contain three alpha helices that coil around one another in a rope like helical structure. The collagen after being secreted in the extracellulat matrix assemble into a polymer forming collagen fibril.Initially pro collagen is formed. after cleavage by proteolytic enzyme they form collagen molecules that assemble in the ECM to collagen fibrils outside the cell.The procollagen before cleavage are assembled in triple helix form in the Endoplasmic reticulum. After amino acids form triple helix, procollagen cleaves the first propeptide and form collagen. When a mutation occur that is improper coiling of procollagen triple helix, the collagen is degraded in the cell and prevent collagen to assemble as collagen fibril by inhibiting cross linkage.

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