Abstract:
The single-stranded DNA binding activity of the Escherichia
coli RecA protein is crucial for homologous recombination to
occur. This and other biochemical activities of ssDNA binding
proteins may be affected by various factors. In this study, we
analyzed the effect of CaCl2, NaCl and NH4NO3 salts in combination
with the pH and nucleotide cofactor effect on the
ssDNA-binding activity of RecA. The studies revealed that, in
addition to the inhibitory effect, these salts exert also a stimulatory
effect on RecA. These effects occur only under very
strict conditions, and the presence or absence and the type of
nucleotide cofactor play here a major role. It was observed
that in contrast to ATP, ATPγS prevented the inhibitory effect
of NaCl and NH4NO3, even at very high salt concentration.
These results indicate that ATPγS most likely stabilizes the
structure of RecA required for DNA binding, making it resistant
to high salt concentrations.