Article

Cleavage of bacteriophage lambda cI repressor involves the RecA C-terminal domain.

Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USA.
Journal of Molecular Biology (impact factor: 4). 12/2008; 385(3):779-87. DOI:10.1016/j.jmb.2008.10.081 pp.779-87
Source: PubMed

ABSTRACT The SOS response to DNA damage in Escherichia coli involves at least 43 genes, all under the control of the LexA repressor. Activation of these genes occurs when the LexA repressor cleaves itself, a reaction catalyzed by an active, extended RecA filament formed on DNA. It has been shown that the LexA repressor binds within the deep groove of this nucleoprotein filament, and presumably, cleavage occurs in this groove. Bacteriophages, such as lambda, have repressors (cI) that are structural homologs of LexA and also undergo self-cleavage when SOS is induced. It has been puzzling that some mutations in RecA that affect the cleavage of repressors are in the C-terminal domain (CTD) far from the groove where cleavage is thought to occur. In addition, it has been shown that the rate of cleavage of cI by RecA is dependent upon both the substrate on which RecA is polymerized and the ATP analog used. Electron microscopy and three-dimensional reconstructions show that the conformation and dynamics of RecA's CTD are also modulated by the polynucleotide substrate and ATP analog. Under conditions where the repressor cleavage rates are the highest, cI is coordinated within the groove by contacts with RecA's CTD. These observations provide a framework for understanding previous genetic and biochemical observations.

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Keywords

Activation
 
ATP analog
 
biochemical observations
 
DNA damage
 
Electron microscopy
 
Escherichia coli
 
LexA repressor
 
LexA repressor binds
 
LexA repressor cleaves
 
mutations
 
nucleoprotein filament
 
polynucleotide substrate
 
reaction catalyzed
 
RecA filament
 
RecA's CTD
 
repressor cleavage rates
 
SOS response
 
structural homologs
 
three-dimensional reconstructions
 
understanding previous genetic