Neuroserpin (NSP, also called proteinase inhibitor 12/PI-12) is an inhibitory member of the serpin family that reacts preferentially with tissue-type plasminogen activator (tPA). It is located in neurons in regions of the brain where tPA is also found, suggesting that neuroserpin is the selective inhibitor of tPA in the central nervous system (CNS). This subgroup corresponds to clade I of the serpin superfamily. 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 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.
Structure:3F5N: Human neuroserpin RCL in open conformation - View structure with Cn3D
Comment:Human neuroserpin crystallizes as a pentamer in the asymmetric unit, but the biological unit is a monomer. Each RCL in the pentamer displays a different conformation, and is involved in pentamerization.
Jiyao W et al.(2023). "The conserved domain database in 2023.",