Enzymatic Activities and DNA Substrate Specificity of Mycobacterium tuberculosis DNA Helicase XPB

摘要: XPB, also known as ERCC3 and RAD25, is a 3′→5′ DNA repair helicase belonging to the superfamily 2 of helicases. XPB an essential core subunit eukaryotic basal transcription factor complex TFIIH. It has two well-established functions: in context damaged DNA, facilitates nucleotide excision by unwinding double stranded (dsDNA) surrounding lesion; while actively transcribing genes, initiation RNA polymerase II at gene promoters. Human other homologs are relatively well characterized compared conserved found mycobacteria archaea. However, more insight into function bacterial helicases central understanding mechanism metabolism pathogenesis general. Here, we Mycobacterium tuberculosis (Mtb XPB), with DNA-dependent ATPase activity. Mtb efficiently catalyzed presence significant excess enzyme. The activity was fueled ATP or dATP Mg2+/Mn2+. Consistent polarity this helicase, enzyme required substrate 3′ overhang 15 nucleotides more. Although unwound model substrates tail, it not active on containing tail. We that ATP-independent annealing complementary strands. These observations significantly enhance our biological roles XPB.