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RecA-mediated cleavage
reaction of Lambda repressor and DNA strand exchange require
an active extended filament conformation but not ATP
hydrolysis
Dieudonné Ndjonka
University of Ngaoundéré, Faculty of Science,
Department of Biological Sciences, P. O. Box 454, Ngaoundéré,
Cameroon. E-mail: dede_ndjonka@yahoo.com. Tel.: 00237 77 05
25 11
Accepted
4 January, 2010 |
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DNA pairing
and strand exchange activities are essential for genetic
recombination. When DNA is damaged, RecA proteins bind to
DNA in the presence of ATP and catalyze the specific
proteolytic cleavage of Lambda repressor. The cleavage
reaction induces and regulates the expression of DNA repair
genes. In this work, it has been examined by introducing
sites directed mutagenesis (in the ATP catalytic domain or
in the DNA binding loop of RecA), the ability of RecA
protein to hydrolyze ATP or to cleave Lambda repressor
either in the presence of DNA or in the presence of high
salt concentration, and the ability of RecA to promote DNA
strand exchange. It was observed that mutant E96D does not
hydrolyze ATP at all, but fulfills RecA functions such as
cleavage of Lambda repressor and strand exchange in the
presence of DNA. However mutant E158K hydrolyzes ATP as well
in the presence of high salt concentration as in the
presence of DNA, but does not fulfill RecA functions. These
observations suggest that ATP hydrolysis is not required for
the cleavage of Lambda repressor and the genetic
recombination, but is necessary for the release of RecA from
DNA before DNA repair.
Key words:
ATP-hydrolysis, genetic recombination, cleavage,
nucleoprotein, DNA repair genes. |
