Nucleoside Triphosphate Pyrophosphohydrolase (EC 3.6.1.8) N-terminal tandem-domain of MazG proteins from Escherichia coli and bacterial homologs
MazG is a NTP-PPase that hydrolyzes all canonical NTPs into their corresponding nucleoside monophosphates and pyrophosphate. The prototype of this family is MazG proteins from Escherichia coli (EcMazG) that represents the most abundant form consisting two sequence-related domains in tandem, this family corresponding to the N-terminal MazG-like domain. EcMazG functions as a regulator of cellular response to starvation by lowering the cellular concentration of guanosine 3',5'-bispyrophosphate (ppGpp). EcMazG exists as a dimer; each monomer contains two tandem MazG-like domains with similarly folded globular structures. However, only the C-terminal domain has well-ordered active site and exhibits an NTPase activity responsible for the regulation of bacterial cell survival under nutritional stress. Divalent ions, such as Mg2+ or Mn2+, are required for activity; however, this domain does not exhibit an NTPase activity despite containing structural features such as the EEXX(E/D) motif and key basic catalytic residues responsible for nucleotide pyrophosphohydrolysis activity. It is suggested that the N-terminal domain of EcMazG might have a house-cleaning function by hydrolyzing noncanonical NTPs whose incorporation into the nascent DNA leads to increased mutagenesis and DNA damage.
Jiyao W et al.(2023). "The conserved domain database in 2023.",