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RSS FeedsCharacterization of Lhr-Core DNA helicase and manganese- dependent DNA nuclease components of a bacterial gene cluster encoding nucleic acid repair enzymes [Enzymology] (Journal of Biological Chemistry)

 
 

11 november 2018 02:00:14

 
Characterization of Lhr-Core DNA helicase and manganese- dependent DNA nuclease components of a bacterial gene cluster encoding nucleic acid repair enzymes [Enzymology] (Journal of Biological Chemistry)
 




Lhr is a large superfamily 2 helicase present in mycobacteria and a moderate range of other bacterial taxa. A shorter version of Lhr, here referred to as Lhr-Core, is distributed widely in bacteria, where it is often encoded in a gene cluster along with predicted binuclear metallo-phosphoesterase (MPE), ATP-dependent DNA ligase, and metallo-?-lactamase exonuclease enzymes. Here we characterized the Lhr-Core and MPE proteins from Pseudomonas putida. We report that P. putida Lhr-Core is an ssDNA-dependent ATPase/dATPase (Km, 0.37 mm ATP; kcat, 3.3 s-1), an ATP-dependent 3-to-5 single-stranded DNA translocase, and an ATP-dependent 3-to-5 helicase. Lhr-Core unwinds 3-tailed duplexes in which the loading/tracking strand is DNA and the displaced strand is either DNA or RNA. We found that P. putida MPE is a manganese-dependent phosphodiesterase that releases p-nitrophenol from bis-p-nitrophenyl phosphate (kcat, 212 s-1) and p-nitrophenyl-5-thymidylate (kcat, 34 s-1) but displays no detectable phosphomonoesterase activity against p-nitrophenyl phosphate. MPE is also a manganese-dependent DNA endonuclease that sequentially converts a closed-circle plasmid DNA to nicked circle and linear forms prior to degrading the linear DNA to produce progressively smaller fragments. The biochemical activities of MPE and a structure predicted in Phyre2 point to MPE as a new bacterial homolog of Mre11. Genetic linkage of a helicase and DNA nuclease with a ligase and a putative exonuclease (a predicted homolog of the SNM1/Apollo family of nucleases) suggests that these enzymes comprise or participate in a bacterial DNA repair pathway.


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26 viewsCategory: Biochemistry
 
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