3crc: Difference between revisions

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'''Crystal Structure of Escherichia coli MazG, the Regulator of Nutritional Stress Response'''

MazG is a nucleoside triphosphate pyrophosphohydrolase that hydrolyzes all canonical nucleoside triphosphates. mazG gene located downstream from mazEF - chromosomal "addiction module", mediated programmed cell death in E. coli. MazG activity is inhibited by MazEF complex both in vivo and in vitro. Enzymatic activity of MazG in vivo affects the cellular level of guanosine 3',5'-bispyrophosphate (ppGpp), synthesized by RelA under amino-acid starvation. The reduction of ppGpp, caused by MazG, may extend the period of cell survival under nutritional stress. Here we describe the first crystal structure of active MazG from E. coli, which is composed of two similarly folded globular domains in tandem. Among two putative catalytic domains, only the Cterminal domain has well-ordered active sites and exhibits an NTPase activity, which are derived from the tightly formed 'additional region'. The MazG-ATP complex structure and subsequent mutagenesis studies explain the peculiar active site environment accommodating all eight canonical NTPs as substrates. In vivo nutrient starvation experiments show that the C-terminus NTPase activity is responsible for the regulation of bacterial cell survival under nutritional stress.

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