title: 5'-Single-stranded/duplex DNA junctions are loading sites for E. coli UvrD translocase.
abstract: Escherichia coli UvrD is a 3'-5' superfamily 1A helicase/translocase involved in a variety of DNA metabolic processes. UvrD can function either as a helicase or only as an single-stranded DNA (ssDNA) translocase. The switch between these activities is controlled in vitro by the UvrD oligomeric state; a monomer has ssDNA translocase activity, whereas at least a dimer is needed for helicase activity. Although a 3'-ssDNA partial duplex provides a high-affinity site for a UvrD monomer, here we show that a monomer also binds with specificity to DNA junctions possessing a 5'-ssDNA flanking region and can initiate translocation from this site. Thus, a 5'-ss-duplex DNA junction can serve as a high-affinity loading site for the monomeric UvrD translocase, whereas a 3'-ss-duplex DNA junction inhibits both translocase and helicase activity of the UvrD monomer. Furthermore, the 2B subdomain of UvrD is important for this junction specificity. This highlights a separation of helicase and translocase function for UvrD and suggests that a monomeric UvrD translocase can be loaded at a 5'-ssDNA junction when translocation activity alone is needed.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Tomko
authors.forename: Haifeng
authors.initials: H
authors.lastname: Jia
authors.forename: Jeehae
authors.initials: J
authors.lastname: Park
authors.forename: Nasib K
authors.initials: NK
authors.lastname: Maluf
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Lohman
mesh_terms: D024506:5' Flanking Region; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; C084217:pcrA protein, Bacteria; C506746:UvrD protein, E coli; D004265:DNA Helicases