title: Crystal structure of Kex1deltap, a prohormone-processing carboxypeptidase from Saccharomyces cerevisiae,.
abstract: Kex1p is a prohormone-processing serine carboxypeptidase found in Saccharomyces cerevisiae. In contrast to yeast serine carboxypeptidase (CPD-Y) and wheat serine carboxypeptidase II (CPDW-II), Kex1p displays a very narrow specificity for lysyl or arginyl residues at the C-terminus of the substrate. The structure of Kex1Deltap, an enzyme that lacks the acidic domain and membrane-spanning portion of Kex1p, has been solved by a combination of molecular replacement and multiple isomorphous replacement and refined to a resolution of 2.4 A. The S1' site of Kex1Deltap is sterically restricted compared to those from CPD-Y or CPDW-II; it also contains two acidic groups that are well positioned to interact with the basic group of a lysine or arginine side chain. The high specificity of Kex1p can therefore be explained by a combination of steric and electronic factors. The structure of the S1 site of Kex1Deltap is also well suited for binding of a lysine or arginine side chain, and the enzyme may therefore exhibit a preference for these residues at P1.
authors.affiliation: Biotechnology Research Institute, National Research Council, 6100 Royalmount Avenue, Montréal, Québec H4P 2R2, Canada.
authors.forename: B H
authors.initials: BH
authors.lastname: Shilton
authors.forename: D Y
authors.initials: DY
authors.lastname: Thomas
authors.forename: M
authors.initials: M
authors.lastname: Cygler
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002268:Carboxypeptidases / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
chemical_list: D002268:Carboxypeptidases; C078874:carboxypeptidase D