کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2189936 | 1096228 | 2006 | 12 صفحه PDF | دانلود رایگان |
Bacillus subtilis bacteriophage SPP1 G40P hexameric replicative DNA helicase unidirectionally translocates with a 5′→3′ polarity while separating the DNA strands. A G40P mutant derivative lacking the N-terminal domain (containing amino acid residues 110–442 from G40P, G40PΔN109) was purified and characterized. G40PΔN109 showed an ATPase activity that was dependent on the presence of single-stranded (ss) DNA. Unlike G40P, G40PΔN109 was shown to bind with similar affinity both ssDNA arms of forked structures by nuclease protection assays. In a pH-dependent manner, G40PΔN109 unwound a branched double-arm substrate preferentially with a 3′→5′ polarity. Our results show that the linker region and the C-terminal domain of G40P are sufficient to render an enzyme capable of encircling the ssDNA tails of the forked DNA and to unwind DNA with both 5′→3′ and 3′→5′ polarity. The presence of the N-terminal domain, which does not play an essential role in helicase action, might be required indirectly for strand discrimination and polarity of translocation.
Journal: Journal of Molecular Biology - Volume 357, Issue 4, 7 April 2006, Pages 1077–1088