Binding of a reduced peptide inhibitor to the aspartic proteinase from Rhizopus chinensis: implications for a mechanism of action.

Abstract
A peptide inhibitor, having the sequence D-His-Pro-Phe-His-Phe.PSI.[CH2-NH]Phe-Val-Tyr, with a reduced bond between the two adjacent phenylalanines, has been diffused into crystals of the aspartic proteinase from Rhizopus chinensis (rhizopuspepsin, EC 3.4.23.6). X-ray diffraction data to 1.8-.ANG. resolution have been collected on the complex, which has been subjected to restrained least-squares refinement to an R-factor (R = .SIGMA..dblvert.Fo