1pjp
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THE 2.2 A CRYSTAL STRUCTURE OF HUMAN CHYMASE IN COMPLEX WITH SUCCINYL-ALA-ALA-PRO-PHE-CHLOROMETHYLKETONE
OverviewOverview
Human chymase (HC) is a chymotrypsin-like serine proteinase expressed by, mast cells. The 2.2 A crystal structure of HC complexed to the peptidyl, inhibitor, succinyl-Ala-Ala-Pro-Phe-chloromethylketone (CMK), was solved, and refined to a crystallographic R-factor of 18.4 %. The HC structure, exhibits the typical folding pattern of a chymotrypsin-like serine, proteinase, and shows particularly similarity to rat chymase 2 (rat mast, cell proteinase II) and human cathepsin G. The peptidyl-CMK inhibitor is, covalently bound to the active-site residues Ser195 and His57; the, peptidyl moiety juxtaposes the S1 entrance frame segment 214-217 by, forming a short antiparallel beta-sheet. HC is a highly efficient, angiotensin-converting enzyme. Modeling of the chymase-angiotensin I, interaction guided by the geometry of the bound chloromethylketone, inhibitor indicates that the extended substrate binding site contains, features that may generate the dipeptidyl carboxypeptidase-like activity, needed for efficient cleavage and activation of the hormone. The, C-terminal carboxylate group of angiotensin I docked into the active-site, cleft, with the last two residues extending beyond the active site, is, perfectly localized to make a favorable hydrogen bond and salt bridge with, the amide nitrogen of the Lys40-Phe41 peptide bond and with the, epsilon-ammonium group of the Lys40 side-chain. This amide positioning is, unique to the chymase-related proteinases, and only chymases from primates, possess a Lys residue at position 40. Thus, the structure conveniently, explains the preferred conversion of angiotensin I to angiotensin II by, human chymase.
About this StructureAbout this Structure
1PJP is a Single protein structure of sequence from Homo sapiens with NAG and ZN as ligands. Active as Chymase, with EC number 3.4.21.39 Full crystallographic information is available from OCA.
ReferenceReference
The 2.2 A crystal structure of human chymase in complex with succinyl-Ala-Ala-Pro-Phe-chloromethylketone: structural explanation for its dipeptidyl carboxypeptidase specificity., Pereira PJ, Wang ZM, Rubin H, Huber R, Bode W, Schechter NM, Strobl S, J Mol Biol. 1999 Feb 12;286(1):163-73. PMID:9931257
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