Cytosolic 5′-Methylthioadenosine/S-Adenosylhomocysteine Nucleosidase MtaN from Mycobacterium. smegmatis: purification, crystallization and X-ray crystallographic analysis

Mycobacterium tuberculosis is a dangerous pathogen, and it can cause the most deadly disease tuberculosis (TB). Nonpathogenic Mycobacterium smegmatis is an important model for studying the M. tuberculosis. M. smegmatis 5’-Methylthioadenosine/S-adenosyl-L-homocysteine nucleosidases (MtaNs) catalyze the hydrolysis of adenine from 5’-methylthioadenosine (MTA), MtaNs cleave the glycosidic bond of MTA or S-adenosylhomocysteine (SAH) irreversibly. In this study, MtaN from M. smegmatis (MsMtaN) was successfully expressed and purified using Ni-NTA affinity, Q anionexchange and gel-filtration chromatography. The protein crystal was obtained and diffracted to a resolution of 2.0 Å. The crystal belonged to the orthorhombic space group P1211, with unit-cell parameters of a =57.6, b = 172.6, and c = 183.3 Å. The Matthews coefficient and solvent content were estimated to be 2.32 ų Da⁻¹ and 47%, respectively, assuming that the asymmetric unit contained only one recombinant protein molecule. Size-exclusion chromatography suggested that MsMtaN prefer to exist as tetramer in solution.