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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

Transforming growth factor β-induced protein (TGFBIp) has been linked to several corneal dystrophies as certain point mutations in the protein may give rise to a progressive accumulation of insoluble protein material in the human cornea. Little is known about the biological functions of this extracellular protein, which is expressed in various tissues throughout the human body. However, it has been found to interact with a number of extracellular matrix macromolecules such as collagens and proteoglycans. Structural information about TGFBIp might prove to be a valuable tool in the elucidation of its function and its role in corneal dystrophies caused by mutations in the TGFBI gene. A simple method for the purification of wild-type and mutant forms of recombinant human TGFBIp from human cells under native conditions is presented here. Moreover, the crystallization and preliminary X-ray analysis of TGFBIp are reported. © 2009 International Union of Crystallography All rights reserved. ; This work was supported by National Eye Institute Grant R01 EY 12712, the Danish National Research Foundation, the Danish Natural Science Research Council, the Danish Association for Prevention of Eye Diseases and Blindness, the Synoptik Foundation, Aarhus University Research Foundation and the Danish Medical Research Council. Further support was provided by BIO2006-02668, PSE-010000-2007-1 and the CONSOLIDER-INGENIO 2010 Project 'La Factoría de Cristalización' (CSD2006-00015) from Spanish public agencies, FP6 Strep Project LSHG-2006-018830 'CAMP' and FPT Collaborative Project 223101 'AntiPathoGN' from the European Union and 2005SGR00280 from the National Catalan Government ; Peer Reviewed