DNA-dependent ATPase activity of bacterial XPB helicases

Tapan Biswas, Jessica M. Pero, Caleb G. Joseph, Oleg V. Tsodikov

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


XPB, the largest subunit of the eukaryotic transcription factor TFIIH, is essential for both initiation of transcription by RNA polymerase II and nucleotide excision repair (NER). XPB belongs to the SF2 superfamily of monomeric helicases. XPB helicase is thought to have evolved in eukaryotes; however, a gene highly homologous to human XPB can be found in a number of bacteria. This report is the first biochemical characterization of XPB homologues from bacteria, specifically those from Mycobacterium tuberculosis and Kineococcus radiotolerans. Similarly to eukaryotic XPB, bacterial XPB are ATP-dependent 3′ → 5′ DNA helicases. The ATPase activity of these XPB helicases is DNA-dependent, requiring a minimum of 4-nucleotide long single-stranded DNA (ssDNA). The maximum rates of ATP hydrolysis are about 10 and 50 molecules per minute by one XPB monomer on a 21-nucleotide ssDNA oligomer and on 5-kb long circular ssDNA, respectively. The ATP hydrolysis by the bacterial XPBs is coupled to their translocation along single-stranded DNA. The hydrolytic activity is strongly dependent on both the nature of a nucleotide triphosphate and that of a divalent metal. The inefficient ATP hydrolysis by bacterial XPB is consistent with nonprocessive functions of its eukaryotic homologue in locally remodeling DNA during transcription initiation and NER.

Original languageEnglish
Pages (from-to)2839-2848
Number of pages10
Issue number12
StatePublished - Mar 31 2009

ASJC Scopus subject areas

  • Biochemistry


Dive into the research topics of 'DNA-dependent ATPase activity of bacterial XPB helicases'. Together they form a unique fingerprint.

Cite this