Observation of ADP-Ribose Pyrophosphatase Reaction in Crystalline-State Induced by Mn（II）Ion Binding

Abstract

ADP-Ribose pyrophosphatase (ADPRase) reaction was observed in crystalline-state at atomic resolutions around 1 Å. ADPRase achieves the general acid-base catalysis in the presence of divalent metal cations. Crystals of ADPRase alone, ADPRase-ADPR binary (ES-state) complex were prepared, and reaction intermediates were captured by the cryo-trapping after the soaking of MnCl₂ into ES-state crystals. Just after two metal binding sites were successively occupied along with the soaking time, ADPR was hydrolyzed and reaction products were released, indicating the completion of the crystalline-state reaction. The key structures of ADPRase-ADPR-two Mn²⁺ ions complex revealed the various enzymatic phenomena including electrostatic, proximity and orientation effects and preferential binding for the transition states. The details of the metal assisting mechanism and the general base catalysis have been discussed.