Mycobacterial MazG is a novel NTP pyrophosphohydrolase involved in oxidative stress response.
MazG nucleoside triphosphate pyrophosphohydrolase (NTP-PPase, EC 3.6.1.8) from the avirulent Mycobacterium tuberculosis H37Ra contains a spontaneous mutation on a highly conserved residue, resulting in an A219E substitution (MtMazG[A219E]). In this work, we show that mycobacterial MazG from either the virulent M. tuberculosis H37Rv (MtMazG) or the fast-growing Mycobacterium smegmatis (MsMazG) is a potent NTP-PPase capable of hydrolyzing all canonical (d)NTPs, as well as the mutagenic dUTP and 8-oxo-7,8-dihydro-2'-dGTP. However, this hydrolysis activity is diminished by the MtMazG[A219E] mutation. Moreover, deletion of mazG in M. smegmatis rendered the mycobacteria defective in response to oxidative stress. Importantly, expression of the wild-type MtMazG, but not the A219E mutant, restored cell viability under oxidative stress. Intriguingly, under oxidative stress, both the mazG-null and MtMazG[A219E]-expressing M. smegmatis strains failed to elevate relA, while retaining their ability to up-regulate sigE, suggesting a specific role for the MazG NTP-PPase activity in oxidative stress-triggered, transcriptional activation of relA. The MtMazG is a homotetramer with each subunit containing a single MazG core domain flanked by two regions, both of which are essential for NTP-PPase activity. Taken together, these results demonstrate that the mycobacterial MazG is a potent NTP-PPase and that this activity is required to maintain the full capacity of the mycobacteria to respond to oxidative stress. Our work implicates a role for the MazG activity in the virulence of M. tuberculosis.
Lu
Liang-dong
LD
State Key Laboratory of Genetic Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai 200433, China.
Sun
Qing
Q
Fan
Xiao-yong
XY
Zhong
Yi
Y
Yao
Yu-feng
YF
Zhao
Guo-Ping
GP
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003848:Deoxyguanine Nucleotides / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D008274:Magnesium / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009161:Mycobacterium / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity; D020102:Mycobacterium smegmatis / Q000201:enzymology / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000201:enzymology / Q000378:metabolism / Q000472:pathogenicity; D018384:Oxidative Stress; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D003848:Deoxyguanine Nucleotides; D029968:Escherichia coli Proteins; C078206:8-oxodeoxyguanosine triphosphate; C543726:MazG protein, E coli; D011755:Pyrophosphatases; C021895:nucleoside triphosphate pyrophosphatase; D008274:Magnesium