Isolation and characterisation of dhel II, a DNA helicase from Drosophila melanogaster embryos stimulated by Escherichia coli-type single-stranded-DNA-binding proteins.
We have purified a DNA helicase from Drosophila embryos by following unwinding activity during the purification of the cellular single-stranded DNA-binding protein dRP-A. This DNA helicase unwinds DNA 5' to 3', has a salt-tolerant activity, and has a preference for purine triphosphates as cofactors for the unwinding reaction. The purified enzyme consists of a single polypeptide of 120 kDa, which cosediments with the helicase activity. Sedimentation analysis suggests that this polypeptide exists as a monomer under high and low salt conditions. Dhel II is able to unwind long stretches of DNA, but with decreased efficiency. Addition of Escherichia coli-like single-stranded DNA-binding proteins stimulates the unwinding activity at least 10-fold on substrates greater than 200 nucleotides. In particular, the mitochondrial single-stranded DNA-binding protein isolated from Drosophila embryos is able to stimulate unwinding by dhel II. These properties show that the helicase described is different from another Drosophila helicase dhel I; it has thus has been classified as dhel II.
Thömmes
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P
Marie Curie Research Institute, The Chart, Oxted, Surrey, England.
Marton
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RF
Cotterill
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D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology; D001483:Base Sequence; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004265:DNA Helicases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D004331:Drosophila melanogaster / Q000196:embryology / Q000201:enzymology*; D004926:Escherichia coli / Q000378:metabolism; D008970:Molecular Weight; D013379:Substrate Specificity
D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D004247:DNA; D004265:DNA Helicases