CRYSTAL-STRUCTURES OF RAT ACID-PHOSPHATASE COMPLEXED WITH THE TRANSITION-STATE ANALOGS VANADATE AND MOLYBDATE - IMPLICATIONS FOR THE REACTION-MECHANISM

The three-dimensional structures of complexes of recombinant rat prostatic acid phosphatase with the transition-state analogs vanadate and molybdate were determined to 0.3-nm resolution using protein crystallographic methods. The overall structure of the enzyme remains unchanged upon binding of the metal oxyanions; only local conformational differences in the positions of some side chains at the active site were found. The metal oxyanions bind in an identical fashion at the active site with trigonal bipyramidal coordination geometry. The metal ion is within coordination distance of the His12 side chain which is located at one of the axial positions. The three equatorial oxygen atoms interact with the conserved residues Arg11, Arg15, Arg79 and His257. Within hydrogen-bonding distance of the axial oxygen atom is the side chain of the conserved residue Asp258. The implications of these results for the catalytic mechanism of acid phosphatase are discussed.