Biochemical characterization of the small isoform of Drosophila melanogaster RECQ5 helicase

Nucleic Acids Res. 2001 Jul 15;29(14):2986-93. doi: 10.1093/nar/29.14.2986.


Recently the gene encoding a member of the RecQ helicase family, RecQ5, was cloned from the fruit fly, Drosophila melanogaster [J.J.Sekelsky, M.H.Brodsky, G.M. Rubin and R.S. Hawley (1999) Nucleic Acids Res., 27, 3762-3769]. The Drosophila RecQ5 transcript is alternatively spliced, like its human counterpart, to yield three protein isoforms. Two of these isoforms are almost identical and have a predicted molecular weight of 54 kDa. The third isoform is larger and contains, in addition to the helicase domain shared by all three isoforms, a long highly charged C-terminal region. A small isoform of the Drosophila RecQ5 protein (RECQ5) has been expressed in Escherichia coli and purified. The purified protein is a single-stranded DNA-stimulated ATPase (dATPase) and a 3'-->5' DNA helicase. Hydrolysis of the nucleotide cofactor is required for unwinding activity and dATP supported the unwinding reaction better than other NTPs. The turnover number for the single-stranded DNA-stimulated dATPase activity was 1380 min(-1), approximately 1.5-fold higher than that observed for the ATPase activity (900 min(-1)). The purified protein catalyzed unwinding of partial duplex substrates up to at least 93 bp, however, unwinding of an 89 bp blunt duplex substrate was not detected.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acid Anhydride Hydrolases / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • DNA Helicases / isolation & purification
  • DNA Helicases / metabolism*
  • Drosophila melanogaster / enzymology*
  • Electrophoresis, Polyacrylamide Gel
  • Hydrolysis
  • Isoenzymes / metabolism
  • Kinetics
  • Nucleic Acid Conformation
  • Nucleoside-Triphosphatase
  • Oligonucleotides / chemistry
  • Oligonucleotides / metabolism
  • RecQ Helicases
  • Substrate Specificity


  • Isoenzymes
  • Oligonucleotides
  • RECQL5 protein, human
  • Adenosine Triphosphate
  • Acid Anhydride Hydrolases
  • Nucleoside-Triphosphatase
  • DNA Helicases
  • RecQ Helicases