Increased DNA unwinding efficiency of bacteriophage T7 DNA helicase mutant protein 4A'/E348K.

The Journal of Biological Chemistry
M T Washington, S S Patel

Abstract

Bacteriophage T7 4A' protein is a DNA helicase that unwinds DNA in a reaction coupled to dTTP hydrolysis. To understand better its mechanism of DNA unwinding, we characterized a set of 4A' mutant proteins (Washington, M. T., Rosenberg, A. H., Griffin, K., Studier, F. W., and Patel, S. S. (1996) J. Biol. Chem. 271, 26825-26834). We showed here, using single turnover DNA unwinding assays, that the 4A'/E348K mutant protein had the unusual property of unwinding DNA (with a 5-6-fold slower rate) despite a significant defect in its dTTPase activity (a 25-30-fold slower rate). Comparing the DNA unwinding rates to the dTTPase rates, we estimated the DNA unwinding efficiencies of both wild-type (about 1 base pair unwound per dTTP hydrolysis) and mutant (4 to 6 base pairs unwound per dTTP hydrolysis). Thus the mutant had a 4-6-fold improvement in its DNA unwinding efficiency over that of the wild-type. We believe that this mutant undergoes less slippage (uncoupled dTTP hydrolysis) than the wild-type. We speculate that nature has selected for a high rate of DNA unwinding rather than a high efficiency of DNA unwinding. Thus even though the mutant is more efficient at DNA unwinding, the wild-type probably was selected because it unwinds DNA...Continue Reading

References

Apr 1, 1992·Journal of Molecular Evolution·T V IlyinaE V Koonin
Jan 1, 1990·Methods in Enzymology·F W StudierJ W Dubendorff
May 5, 1986·Journal of Molecular Biology·F W Studier, B A Moffatt
Aug 1, 1981·Proceedings of the National Academy of Sciences of the United States of America·T L Hill, T Tsuchiya
Aug 25, 1995·The Journal of Biological Chemistry·S M NotarnicolaC C Richardson
Apr 25, 1995·Proceedings of the National Academy of Sciences of the United States of America·E H EgelmanS S Patel
Jan 1, 1996·Annual Review of Biochemistry·T M Lohman, K P Bjornson
Nov 28, 1996·Nature·H S SubramanyaD B Wigley
May 13, 1997·Proceedings of the National Academy of Sciences of the United States of America·M M HingoraniS S Patel

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Citations

Mar 31, 2010·Proceedings of the National Academy of Sciences of the United States of America·Ajit K SatapathyCharles C Richardson
Aug 29, 2006·Nucleic Acids Research·Ilker Donmez, Smita S Patel
May 15, 2007·Biochimica Et Biophysica Acta·Ping Xie
Aug 31, 2000·Annual Review of Biochemistry·S S Patel, K M Picha
Dec 10, 1999·The Journal of Biological Chemistry·D N Frick, C C Richardson
Dec 10, 1999·The Journal of Biological Chemistry·D N FrickC C Richardson
May 4, 2006·The Journal of Biological Chemistry·Smita S Patel, Ilker Donmez

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