Nucleic Acids Research Advance Access originally published online on August 30, 2007
Nucleic Acids Research 2007 35(18):6029-6041; doi:10.1093/nar/gkm544
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Nucleic Acids Research, 2007, Vol. 35, No. 18 6029-6041
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Structural Biology |
The arginine finger of the Bloom syndrome protein: its structural organization and its role in energy coupling
1School of Life Science, East China Normal University, Science Bld., 3663 North Zhongshan Rd., Shanghai 200062, P. R. China, 2Biophysics Laboratory, Department of Physics, Renmin University, Beijing, China, 3CNRS, UMR 2027, Institut Curie - Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, France, 4Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China and 5LBPA, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France.
*To whom correspondence should be addressed. Tel: +33 1 69 86 31 81; Fax: +33 1 69 86 94 29; Email: xu-guang.xi{at}curie.u-psud.fr
Received March 27, 2007. Revised June 19, 2007. Accepted July 4, 2007.
RecQ family helicases are essential in maintaining chromosomal DNA stability and integrity. Despite extensive studies, the mechanisms of these enzymes are still poorly understood. Crystal structures of many helicases reveal a highly conserved arginine residue located near the 
-phosphate of ATP. This residue is widely recognized as an arginine finger, and may sense ATP binding and hydrolysis, and transmit conformational changes. We investigated the existence and role of the arginine finger in the Bloom syndrome protein (BLM), a RecQ family helicase, in ATP hydrolysis and energy coupling. Our studies by combination of structural modelling, site-directed mutagenesis and biochemical and biophysical approaches, demonstrate that mutations of residues interacting with the -phosphate of ATP or surrounding the ATP-binding sites result in severe impairment in the ATPase activity of BLM. These mutations also impair BLM's DNA-unwinding activities, but do not affect its ATP and DNA-binding abilities. These data allow us to identify R982 as the residue that functions as a BLM arginine finger. Our findings further indicate how the arginine finger is precisely positioned by the conserved motifs with respect to the -phosphate.