PMID: 8471620Apr 20, 1993Paper

Kinetics of Escherichia coli helicase II-catalyzed unwinding of fully duplex and nicked circular DNA

Biochemistry
G T Runyon, T M Lohman

Abstract

Escherichia coli helicase II (UvrD) protein can initiate unwinding of duplex DNA at blunt ends or nicks, although these reactions require excess protein. We have undertaken kinetic studies of these reactions in order to probe the mechanism of initiation of unwinding. DNA unwinding was monitored directly by using agarose gel electrophoresis and indirectly through the rate of ATP hydrolysis by helicase II in the presence of an ATP-regenerating system. In the presence of fully duplex DNA and excess helicase II, the rate of ATP hydrolysis displays a distinct lag phase before the final steady-state rate of hydrolysis is reached. This reflects the fact that ATP hydrolysis under these conditions results from helicase II binding to the ssDNA products of the unwinding reaction, rather than from an intrinsic duplex DNA-dependent ATPase activity. Unwinding of short blunt-ended duplex DNA (341 and 849 base pairs) occurs in an "all-or-none" reaction, indicating that initiation of unwinding by helicase II is rate-limiting. We propose a minimal mechanism for the initiation of DNA unwinding by helicase II which includes a binding step followed by the rate-limiting formation of an initiation complex, possibly involving protein dimerization, and...Continue Reading

Citations

Jan 1, 1996·Protein Science : a Publication of the Protein Society·E V Koonin, K E Rudd
Jul 29, 2011·Biochemistry·Anita Niedziela-MajkaTimothy M Lohman
Jan 24, 2012·The Journal of Biological Chemistry·Annamarie S CarterSteven W Matson
Aug 29, 2006·Nucleic Acids Research·Steven W Matson, Adam B Robertson
Sep 27, 2000·Journal of Bacteriology·G F MoolenaarN Goosen
Sep 30, 2010·The EMBO Journal·Eric J TomkoTimothy M Lohman
May 16, 1998·The Journal of Biological Chemistry·M YamaguchiP Modrich
Apr 1, 2015·Nucleic Acids Research·Vessela PetrovaMichael M Cox
Feb 20, 2008·The Journal of Biological Chemistry·Bartek SikoraKevin D Raney
May 23, 2012·PloS One·Adeyemi O AdedejiStefan G Sarafianos
Jun 22, 2001·The Journal of Biological Chemistry·G W RogersW C Merrick
Jun 5, 2018·Journal of Molecular Biology·Jiaquan LiuRichard Fishel

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