serpin family proteins from crustaceans, chelicerates, and insects
This group includes a variety of serpins from crustaceans (sea louse, Chinese mitten crab, signal crayfish, red king crab, Asian tiger shrimp), chelicerates (Atlantic horseshoe crab, common house spider), and insects (Asian tiger mosquito, caddisfly, pea aphid, bed bug, fruit fly, Australian sheep blowfly, tobacco hornworm, alfalfa leafcutting bee). 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 have been associated with 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.
Comment:depending on the conformational state, the RC loop is surface accessible in the active form or buried and inserted as the central beta strand in the inactive form.
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