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Báo cáo khoa học: Structure of peptidase T from Salmonella typhimurium

The structure of peptidase T, or tripeptidase, was deter-mined by multiple wavelength anomalous dispersion (MAD) methodology and re®ned to 2.4 A Ê resolution. Pep-tidase T comprises two domains; a catalytic domainwith an active site containing two metal ions, and a smaller domain formed through a long insertion into the catalytic domain. The twometal ions, presumablyzinc, are separatedby3.3 AÊ , and are coordinated by ®ve carboxylate and histidine ligands. | Eur. J. Biochem. 269 443-450 2002 FEBS 2002 Structure of peptidase T from Salmonella typhimurium Kjell Hakansson and Charles G. Miller Department of Microbiology University of Illinois at Urbana-Champaign Urbana IL USA The structure of peptidase T or tripeptidase was determined by multiple wavelength anomalous dispersion MAD methodology and refined to 2.4 A resolution. Peptidase T comprises two domains a catalytic domain with an active site containing two metal ions and a smaller domain formed through a long insertion into the catalytic domain. The two metal ions presumably zinc are separated by 3.3 A and are coordinated by five carboxylate and histidine ligands. The molecular surface of the active site is negatively charged. Peptidase T has the same basic fold as carboxypeptidase G2. When the structures of the two enzymes are superimposed a number of homologous residues not evi dent from the sequence alone could be identified. Comparison of the active sites of peptidase T carboxypeptidase G2 Aeromonas proteolytica aminopeptidase carboxypeptidase A and leucine aminopeptidase reveals a common structural framework with interesting similarities and differences in the active sites and in the zinc coordination. A putative binding site for the C-terminal end of the tripeptide substrate was found at a peptidase T specific fingerprint sequence motif. Keywords tripeptidase aminotripeptidase metallopep-tidase X-ray crystallography MAD. Escherichia coli and Salmonella typhimurium express several intracellular enzymes capable of hydrolyzing peptides 1 . Many of these enzymes have been shown to function in the degradation of intracellular proteins and in the catabolism of exogenously supplied peptides 2 . One of these enzymes peptidase T or tripeptidase EC 3.4.11.- is a 409 aminoacid metalloenzyme that hydrolyzes tripeptides at their N-termini 3 4 . The enzymatic activity of the S. typhimurium enzyme is both specific and unusual dipeptides tetrapeptides or tripeptides with .