To: Icebrg who wrote (2031 ) 2/3/2004 4:35:03 PM From: tuck Respond to of 3044 [MLN 4760: ACE2 inhibitor for SARS and cardiovascular indications] >>J Biol Chem. 2004 Jan 30 [Epub ahead of print] ACE2 structures reveal a large hinge-bending motion important for inhibitor binding and catalysis. Towler P, Staker B, Prasad SG, Menon S, Tang J, Parsons T, Ryan D, Fisher M, Williams D, Dales NA, Patane MA, Pantoliano MW. Drug Discovery, Millennium Pharmaceuticals Inc., Cambridge, MA 02139. The angiotensin converting enzyme-related carboxypeptidase, ACE2, is a type I integral membrane protein of 805 amino acids that contains one HEXXH + E zinc-binding consensus sequence. ACE2 has been implicated in the regulation of heart function, and also, as a functional receptor for the coronavirus that causes the severe acute respiratory syndrome (SARS). To gain further insights into this enzyme, the first crystal structures of the native and inhibitor-bound forms of the ACE2 extracellular domains were solved to 2.2 and 3.0 resolution, respectively. Comparison of these structures revealed a large inhibitor dependent hinge bending movement of one catalytic subdomain relative to the other (~16), which brings important residues into position for catalysis. The binding of the potent inhibitor, (S,S) 2-{1-carboxy-2-[3-(3,5-dichloro-benzyl)-3H-imidazol-4-yl]-ethylamino}-4-methyl-pentanoic acid (MLN-4760), makes key binding interactions within the active site, and offers insights regarding the action of residues involved in catalysis and substrate specificity. A few active site residue substitutions for ACE2, relative to ACE, appear to eliminate the S2 substrate binding subsite, and account for the observed reactivity change from the peptidyl-dipeptidase activity of ACE to the carboxypeptidase activity of ACE2.<< The full text is available for free in PDF format:jbc.org Cheers, Tuck