title: Inhibitor coordination interactions in the binuclear manganese cluster of arginase.
abstract: Arginase is a manganese metalloenzyme that catalyzes the hydrolysis of L-arginine to form L-ornithine and urea. The structure and stability of the binuclear manganese cluster are critical for catalytic activity as it activates the catalytic nucleophile, metal-bridging hydroxide ion, and stabilizes the tetrahedral intermediate and its flanking states. Here, we report X-ray structures of a series of inhibitors bound to the active site of arginase, and each inhibitor exploits a different mode of coordination with the Mn(2+)(2) cluster. Specifically, we have studied the binding of fluoride ion (F(-); an uncompetitive inhibitor) and L-arginine, L-valine, dinor-N(omega)-hydroxy-L-arginine, descarboxy-nor-N(omega)-hydroxy-L-arginine, and dehydro-2(S)-amino-6-boronohexanoic acid. Some inhibitors, such as fluoride ion, dinor-N(omega)-hydroxy-L-arginine, and dehydro-2(S)-amino-6-boronohexanoic acid, cause the net addition of one ligand to the Mn(2+)(2) cluster. Other inhibitors, such as descarboxy-nor-N(omega)-hydroxy-L-arginine, simply displace the metal-bridging hydroxide ion of the native enzyme and do not cause any net change in the metal coordination polyhedra. The highest affinity inhibitors displace the metal-bridging hydroxide ion (and sometimes occupy a Mn(2+)(A) site found vacant in the native enzyme) and maintain a conserved array of hydrogen bonds with their alpha-amino and -carboxylate groups.
authors.affiliation: Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
authors.forename: Evis
authors.initials: E
authors.lastname: Cama
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Pethe
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Boucher
authors.forename: Shoufa
authors.initials: S
authors.lastname: Han
authors.forename: Frances A
authors.initials: FA
authors.lastname: Emig
authors.forename: David E
authors.initials: DE
authors.lastname: Ash
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Viola
authors.forename: Daniel
authors.initials: D
authors.lastname: Mansuy
authors.forename: David W
authors.initials: DW
authors.lastname: Christianson
mesh_terms: D000818:Animals; D001119:Arginase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D001120:Arginine / Q000031:analogs & derivatives / Q000737:chemistry; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry; D006860:Hydrogen Bonding; D008345:Manganese; D008667:Metalloproteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D015394:Molecular Structure; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins; D014633:Valine / Q000737:chemistry
chemical_list: D004791:Enzyme Inhibitors; D008667:Metalloproteins; D011994:Recombinant Proteins; D005461:Fluorine; D008345:Manganese; D001120:Arginine; D001119:Arginase; D014633:Valine