Functional characterization of COG1713 (YqeK) as a novel diadenosine tetraphosphate hydrolase family
Abstract
Diadenosine tetraphosphate (Ap4A) is a dinucleotide found in both prokaryotes and eukaryotes. In bacteria, its cellular level increases following exposure to various stress signals and stimuli, and its accumulation is generally correlated to increased sensitivity to the stressful condition, decreased pathogenicity, and enhanced antibiotic susceptibility. Ap4A is produced as a byproduct of tRNA aminoacylation, and it is cleaved to ADP molecules by hydrolases of the ApaH and Nudix families and/or by specific phosphorylases. Here, starting from the evidence that the recombinant protein YqeK from Staphylococcus aureus copurified with ADP, and aided by thermal shift and kinetic analyses, we identified the YqeK family of proteins (COG1713) as an unprecedented class of symmetrically-cleaving Ap4A hydrolases. We validated the functional assignment by confirming YqeK ability to affect the in vivo level of Ap4A in B. subtilis YqeK shows a catalytic efficiency towards Ap4A similar to that of the symmetrically-cleaving Ap4A hydrolases of the known ApaH family, although it displays a distinct fold, typical of proteins of the HD domain superfamily that harbor a diiron cluster. Analysis of the available 3D structures of three members of the Y...Continue Reading
References
The ObgE/CgtA GTPase influences the stringent response to amino acid starvation in Escherichia coli.
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