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Journal of Nucleic Acids
Volume 2012, Article ID 392039, 8 pages
Research Article

Structural and Functional Characterization of RecG Helicase under Dilute and Molecular Crowding Conditions

1Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 7-1-20 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan
2Amity Institute of Biotechnology, Amity University Uttar Pradesh, Sector-125, Expressway Highway, Noida 201303, India
3Department of Nanobiochemistry, Faculty of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, 7-1-20 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan

Received 4 April 2012; Accepted 30 May 2012

Academic Editor: Masayasu Kuwahara

Copyright © 2012 Sarika Saxena et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In an ATP-dependent reaction, the Escherichia coli RecG helicase unwinds DNA junctions in vitro. We present evidence of a unique protein conformational change in the RecG helicase from an α-helix to a β-strand upon an ATP binding under dilute conditions using circular dichroism (CD) spectroscopy. In contrast, under molecular crowding conditions, the α-helical conformation was stable even upon an ATP binding. These distinct conformational behaviors were observed to be independent of Na+ and Mg2+. Interestingly, CD measurements demonstrated that the spectra of a frayed duplex decreased with increasing of the RecG concentration both under dilute and molecular crowding conditions in the presence of ATP, suggesting that RecG unwound the frayed duplex. Our findings raise the possibility that the α-helix and β-strand forms of RecG are a preactive and an active structure with the helicase activity, respectively.