The molecular structure and catalytic mechanism of a novel carboxyl peptidase from Scytalidium lignicolum
AUTOR(ES)
Fujinaga, Masao
FONTE
National Academy of Sciences
RESUMO
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 (Rfree = 0.246) at 2.1-Å 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 β-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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=373467Documentos Relacionados
- Molecular architecture and assembly mechanism of Drosophila tripeptidyl peptidase II
- Structure and mechanism of action of a novel phosphoglycerate mutase from Bacillus stearothermophilus
- Crystal Structure and Catalytic Mechanism of 4-Methylmuconolactone Methylisomerase*
- Crystal structure of the outer membrane protease OmpT from Escherichia coli suggests a novel catalytic site
- Structure and Catalytic Mechanism of the Thioesterase CalE7 in Enediyne Biosynthesis*