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.
State Key Laboratory of Genetic Engineering, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai 200433, China.
Liang-dong
LD
Lu
Qing
Q
Sun
Xiao-yong
XY
Fan
Yi
Y
Zhong
Yu-feng
YF
Yao
Guo-Ping
GP
Zhao
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