Structure and mechanism of MT-ADPRase, a Nudix hydrolase from Mycobacterium tuberculosis

Nudix hydrolases are a family of proteins that contain the characteristic sequence GX₅EX₇REUXEEXG(I/L/V), the Nudix box. They catalyze the hydrolysis of a variety of nucleoside diphosphate derivatives such as ADP-ribose, Ap_nA (3 ≤ n ≤ 6), NADH, and dATP. A number of Nudix hydrolases from several species, ranging from bacteria to humans, have been characterized, including, in some cases, the determination of their three-dimensional structures. The product of the Rv1700 gene of M. tuberculosis is a Nudix hydrolase specific for ADP-ribose (ADPR). We have determined the crystal structures of MT-ADPRase alone, and in complex with substrate, with substrate and the nonactivating metal ion Gd³⁺, and in complex with a nonhydrolyzable ADPR analog and the activating metal ion Mn²⁺. These structures, refined with data extending to resolutions between 2.0 and 2.3 Å, showed that there are sequence differences in binding site residues between MT-ADPRase and a human homolog that may be exploited for antituberculosis drug development.