1s2k
Structure of SCP-B a member of the Eqolisin family of Peptidases in a complex with a Tripeptide Ala-Ile-His
OverviewOverview
The molecular structure of the pepstatin-insensitive carboxyl peptidase from Scytalidium lignicolum, formerly known as scytalidopepsin B, was solved by multiple isomorphous replacement phasing methods and refined to an R factor of 0.230 (R(free) = 0.246) at 2.1-A resolution. In addition to the structure of the unbound peptidase, the structure of a product complex of cleaved angiotensin II bound in the active site of the enzyme was also determined. We propose the name scytalidocarboxyl peptidase B (SCP-B) for this enzyme. On the basis of conserved, catalytic residues identified at the active site, we suggest the name Eqolisin for the enzyme family. The previously uninvestigated SCP-B fold is that of a beta-sandwich; each sheet has seven antiparallel strands. A tripeptide product, Ala-Ile-His, bound in the active site of SCP-B has allowed for identification of the catalytic residues and the residues in subsites S1, S2, and S3, which are important for substrate binding. The most likely hydrolytic mechanism involves nucleophilic attack of a general base (Glu-136)-activated water (OH(-)) on the si-face of the scissile peptide carbonylcarbon atom to form a tetrahedral intermediate. Electrophilic assistance and oxyanion stabilization is provided by the side-chain amide of Gln-53. Protonation of the leaving-group nitrogen is accomplished by the general acid function of the protonated carboxyl group of Glu-136.
About this StructureAbout this Structure
1S2K is a Single protein structure of sequence from Scytalidium lignicola. Full crystallographic information is available from OCA.
ReferenceReference
The molecular structure and catalytic mechanism of a novel carboxyl peptidase from Scytalidium lignicolum., Fujinaga M, Cherney MM, Oyama H, Oda K, James MN, Proc Natl Acad Sci U S A. 2004 Mar 9;101(10):3364-9. Epub 2004 Mar 1. PMID:14993599 Page seeded by OCA on Sat May 3 08:13:09 2008