Mycobacterium smegmatis RqlH defines a novel clade of bacterial RecQ-like DNA helicases with ATP-dependent 3'-5' translocase and duplex unwinding activities

Nucleic Acids Res. 2012 May;40(10):4604-14. doi: 10.1093/nar/gks046. Epub 2012 Jan 28.

Abstract

The Escherichia coli RecQ DNA helicase participates in a pathway of DNA repair that operates in parallel to the recombination pathway driven by the multisubunit helicase-nuclease machine RecBCD. The model mycobacterium Mycobacterium smegmatis executes homologous recombination in the absence of its helicase-nuclease machine AdnAB, though it lacks a homolog of E. coli RecQ. Here, we identify and characterize M. smegmatis RqlH, a RecQ-like helicase with a distinctive domain structure. The 691-amino acid RqlH polypeptide consists of a RecQ-like ATPase domain (amino acids 1-346) and tetracysteine zinc-binding domain (amino acids 435-499), separated by an RqlH-specific linker. RqlH lacks the C-terminal HRDC domain found in E. coli RecQ. Rather, the RqlH C-domain resembles bacterial ComF proteins and includes a phosphoribosyltransferase-like module. We show that RqlH is a DNA-dependent ATPase/dATPase that translocates 3'-5' on single-stranded DNA and has 3'-5' helicase activity. These functions inhere to RqlH-(1-505), a monomeric motor unit comprising the ATPase, linker and zinc-binding domains. RqlH homologs are distributed widely among bacterial taxa. The mycobacteria that encode RqlH lack a classical RecQ, though many other Actinobacteria have both RqlH and RecQ. Whereas E. coli K12 encodes RecQ but lacks a homolog of RqlH, other strains of E. coli have both RqlH and RecQ.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / classification
  • Bacterial Proteins / metabolism*
  • DNA / metabolism
  • DNA, Single-Stranded / metabolism
  • Kinetics
  • Metals / metabolism
  • Molecular Sequence Data
  • Mycobacterium smegmatis / enzymology*
  • Phylogeny
  • Protein Structure, Tertiary
  • RecQ Helicases / chemistry
  • RecQ Helicases / classification*
  • RecQ Helicases / metabolism*
  • Substrate Specificity

Substances

  • Bacterial Proteins
  • DNA, Single-Stranded
  • Metals
  • Adenosine Triphosphate
  • DNA
  • RecQ Helicases