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Helicases play essential roles in nearly all DNA metabolic transactions and have been implicated in a variety of human genetic disorders. A hallmark of these enzymes is the existence of a set of highly conserved amino acid sequences termed the 'helicase motifs' that were hypothesized to be critical for helicase function. These motifs are shared by another(More)
Helicases are thought to function as oligomers (generally dimers or hexamers). Here we demonstrate that although Escherichia coli DNA helicase II (UvrD) is capable of dimerization as evidenced by a positive interaction in the yeast two-hybrid system, gel filtration chromatography, and equilibrium sedimentation ultracentrifugation (Kd = 3.4 microM), the(More)
Escherichia coli helicase II, product of the uvrD gene, is a single-stranded DNA-dependent nucleoside 5'-triphosphatase with helicase activity. As a DNA-dependent ATPase, helicase II translocates processively along single-stranded DNA (S. W. Matson, unpublished results). The direction of translocation has been determined using a helicase assay that directly(More)
The F plasmid TraI protein (DNA helicase I) plays an essential role in conjugative DNA transfer as both a transesterase and a helicase. Previous work has shown that the 192-kDa TraI protein is a highly processive helicase, catalytically separating >850 bp under steady-state conditions. In this report, we examine the kinetic mechanism describing DNA(More)
The F-plasmid-encoded TraI protein, also known as DNA helicase I, is a bifunctional protein required for conjugative DNA transfer. The enzyme catalyzes two distinct but functionally related reactions required for the DNA processing events associated with conjugation: the site- and strand-specific transesterification (relaxase) reaction that provides the(More)
DNA helicases catalyze the disruption of the hydrogen bonds that hold the two strands of double-stranded DNA together. This energy-requiring unwinding reaction results in the formation of the single-stranded DNA required as a template or reaction intermediate in DNA replication, repair and recombination. A combination of biochemical and genetic studies have(More)
The Saccharomyces cerevisiae RAD3 gene, which is required for cell viability and excision repair of damaged DNA, encodes an 89-kDa protein that has a single-stranded DNA-dependent ATPase activity. We now show that the RAD3 protein also possesses a helicase activity that unwinds duplex regions in DNA substrates constructed by annealing DNA fragments of(More)
Escherichia coli helicase II has been purified to near homogeneity from cells harboring a multicopy plasmid containing the structural gene for helicase II, uvrD. In this paper a detailed description of the single-stranded DNA-dependent nucleoside 5'-triphosphatase and helicase reactions catalyzed by helicase II is presented. The results of this study(More)
The gene 4 protein of bacteriophage T7 is both a primase and a helicase. In this paper, we present a detailed description of a third activity, single-stranded DNA-dependent nucleoside 5'-triphosphate hydrolysis, and show that this activity is coupled to the unidirectional translocation of the gene 4 protein on single-stranded DNA (Tabor, S., and Richardson,(More)