serpin family H member 1, collagen-binding protein 1
Collagen-binding protein 1 (CBP1, also called heat shock protein 47/hsp47 or colligin), because of its collagen binding ability, is a chaperone specific protein for the correct folding of types I-V procollagen in the endoplasmic reticulum (ER). It is induced under stress conditions through heat shock element-heat shock factor interaction and has been shown to be essential for collagen biosynthesis. Hsp47 transiently binds to procollagen in the ER, dissociates in the cis-Golgi or ER-Golgi intermediate compartment, and is then transported back to the ER via its RDEL retention sequence. Hsp47 recognizes collagenous (Gly-Xaa-Arg) repeats on triple-helical procollagen and can prevent local unfolding and/or aggregate formation of procollagen. Hsp47 is a non-inhibitory member of the SERPIN superfamily and corresponds to clade H. In general, SERine Proteinase INhibitors (serpins) exhibit conformational polymorphism shifting from native to cleaved, latent, delta, or polymorphic forms. Many serpins, such as antitrypsin and antichymotrypsin, function as serine protease inhibitors which regulate blood coagulation cascades. Non-inhibitory serpins perform many diverse functions such as chaperoning proteins or transporting hormones. Serpins are of medical interest because mutants can cause blood clotting disorders, emphysema, cirrhosis, and dementia. A classification based on evolutionary relatedness has resulted in the assignment of serpins to 16 clades designated A-P along with some orphans.
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