Crystal and molecular structure of the XXXX proteinase inhibitor CI-2 from @entity2247 seeds.

@entity2247 @entity563 @entity3884 @entity415 @entity367 @entity1520
Chymotrypsin inhibitor 2 (CI-2), a @entity563 proteinase inhibitor from @entity2247 seeds, has been crystallized and its three-dimensional structure determined at 2.0-A resolution by the molecular replacement method. The structure has been refined by restrained-parameter least-squares methods to a crystallographic R factor (= sigma parallel Fo magnitude of-Fo parallel/sigma magnitude of Fo) o of 0.198. CI-2 is a member of the @entity415 inhibitor 1 family. It lacks the characteristic stabilizing @entity1520 bonds of most other members of @entity563 proteinase inhibitor families. The body of CI-2 shows few conformational changes between the free inhibitor and the previously reported structure of CI-2 in complex with subtilisin Novo [McPhalen, C.A., Svendsen, I., Jonassen, I., _ James, M.N.G. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 7242-7246]. However, the reactive site loop has some significant conformational differences between the free inhibitor and its complexed form. The residues in this segment of polypeptide exhibit relatively large thermal motion parameters and some disorder in the uncomplexed form of the inhibitor. The reactive site bond is between Met-59I and @entity367 -60I in the consecutive sequential numbering of CI-2 (Met-60- @entity367 -61 according to the alignment of Svendsen et al. [Svendsen, I., Hejgaard, J., _ Chavan, J.K. (1984) Carlsberg Res. Commun. 49, 493-502]). The network of @entity3884 bonds and electrostatic interactions stabilizing the conformation of the reactive site loop is much less extensive in the free than in the complexed inhibitor.
