DNA 3'-5' translocase XPB2

UniProtKB accession:  Q970I2

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UniProtKB description:  ATP-dependent DNA translocase which moves along double-stranded DNA (dsDNA) in a 3'-5' direction, unwinding the DNA (PubMed:32986831, PubMed:37874269). The ThM domain grips the resulting 3'-ssDNA tail and functions as a wedge (particularly Phe-278), breaking dsDNA base pairs, probably using the energy from ATP hydrolysis to move along dsDNA (PubMed:32986831). A DNA-dependent ATPase; double-stranded DNA (dsDNA) stimulates the activity more than single-stranded DNA (ssDNA), while Bax1 stimulates ATPase more (PubMed:21132514, PubMed:32986831). In an in vitro assay had no detectable helicase activity (PubMed:21132514). Binds ssDNA better than dsDNA (PubMed:21132514). Has very low ATPase activity that is stimulated by Bax1; dsDNA, Y-form DNA and a DNA substrate with a 6 base pair (bp) bubble in the center stimulate the XPB2-Bax1 ATPase activity about 10- 20-fold more than the absence of DNA (PubMed:32374860, PubMed:32986831). In an XPB2-Bax1-bubble DNA crystal (12 bp of dsDNA, a 6 base bubble and 6 bp of dsDNA) the short 6 bp arm is unwound. The 2 helicase and the ThM domains of XPB2 with the NTD and CRD domains of Bax1 encircle the DNA, forming a tunnel where the 12 bp dsDNA and the ds-ssDNA junction are located (PubMed:32986831). The ThM domain is wedged between the ssDNA tails, with the 5' ssDNA contacting Bax1 and the 3' ssDNA in a channel in XPB2 (PubMed:32986831). Bax1 increases the affinity of XPB2 for forked DNA (PubMed:32986831).