Suchergebnisse

Trypanosoma cruzi is the aetiological agent of Chagas' disease, a chronic infection that affects millions in Central and South America. Proteolytic enzymes are involved in the development and progression of this disease and two metallocarboxypeptidases, isolated from T. cruzi CL Brener clone, have recently been characterized: TcMCP-1 and TcMCP-2. Although both are cytosolic and closely related in sequence, they display different temporary expression patterns and substrate preferences. TcMCP-1 removes basic C-terminal residues, whereas TcMCP-2 prefers hydrophobic/aromatic residues. Here we report the three-dimensional structure of TcMCP-1. It resembles an elongated cowry, with a long, deep, narrow active-site cleft mimicking the aperture. It has an N-terminal dimerization subdomain, involved in a homodimeric catalytically active quaternary structure arrangement, and a proteolytic subdomain partitioned by the cleft into an upper and a lower moiety. The cleft accommodates a catalytic metal ion, most likely a cobalt, which is co-ordinated by residues included in a characteristic zinc-binding sequence, HEXXH and a downstream glutamate. The structure of TcMCP-1 shows strong topological similarity with archaeal, bacterial and mammalian metallopeptidases including angiotensin-converting enzyme, neurolysin and thimet oligopeptidase. A crucial residue for shaping the S1′ pocket in TcMCP-1, Met-304, was mutated to the respective residue in TcMCP-2, an arginine, leading to a TcMCP-1 variant with TcMCP-2 specificity. The present studies pave the way for a better understanding of a potential target in Chagas' disease at the molecular level and provide a template for the design of novel therapeutic approaches. © 2008 The Authors. ; This study was supported by the following grants: BIO2006-02668, BFU2006-09593, BIO2007-68046, PSE-010000-2007-1 and the CONSOLIDER-INGENIO 2010 Project 'La Factoría de Cristalización' (CSD2006-00015) from Spanish public agencies; EU FP6 Strep Project LSHG- 2006–018830 'CAMP'; EU FP7 Collaborative Project 223101 'AntiPathoGN'; 2005SGR00280 and 2005SGR01027 from the National Catalan Government; and PICT2003 01–15042 from the Agencia Nacional de Promoción Científica y Tecnológica, Ministerio de Ciencia, Tecnología e Innovación Productiva, Argentina. We acknowledge the help provided by European Synchrotron Radiation Facility local contacts. Funding for data collection was provided by the facility ; Peer Reviewed

The only endogenous protein inhibitor known for metallocarboxypeptidases (MCPs) is latexin, a 25-kDa protein discovered in the rat brain. Latexin, alias endogenous carboxypeptidase inhibitor, inhibits human CPA4 (hCPA4), whose expression is induced in prostate cancer cells after treatment with histone deacetylase inhibitors. hCPA4 is a member of the A/B subfamily of MCPs and displays the characteristic α/β-hydrolase fold. Human latexin consists of two topologically equivalent subdomains, reminiscent of cystatins, consisting of an α-helix enveloped by a curved β-sheet. These subdomains are packed against each other through the helices and linked by a connecting segment encompassing a third α-helix. The enzyme is bound at the interface of these subdomains. The complex occludes a large contact surface but makes rather few contacts, despite a nanomolar inhibition constant. This low specificity explains the flexibility of latexin in inhibiting all vertebrate A/B MCPs tested, even across species barriers. In contrast, modeling studies reveal why the N/E subfamily of MCPs and invertebrate A/B MCPs are not inhibited. Major differences in the loop segments shaping the border of the funnel-like access to the protease active site impede complex formation with latexin. Several sequences ascribable to diverse tissues and organs have been identified in vertebrate genomes as being highly similar to latexin. They are proposed to constitute the latexin family of potential inhibitors. Because they are ubiquitous, latexins could represent for vertebrate A/B MCPs the counterparts of tissue inhibitors of metalloproteases for matrix metalloproteinases. © 2005 by The National Academy of Sciences of the USA. ; This work was supported by Spanish Ministry for Science and Technology Grants BIO2003-00132, GEN2003-20642, and BIO2001-2046 and >Fundación La Caixa> Grant ON03-7-0. Further support was provided by Commission of the European Communities Grant LSHC-CT-2003-503297 >CANCERDEGRADOME>. For data collections, funding was provided by the European Synchroton Radiation Facility and by the European Union Grant RII3-CT-2004-506008 ; Peer Reviewed