Abstract
The RecX protein is a potent inhibitor of RecA activities. We identified several factors that affect RecX-RecA interaction. The interaction is enhanced by the RecA C terminus and by significant concentrations of free Mg(2+) ion. The interaction is also enhanced by an N-terminal His(6) tag on the RecX protein. We conclude that RecX protein interacts most effectively with a RecA functional state designated A(o) and that the RecA C terminus has a role in modulating the interaction. We further identified a C-terminal point mutation in RecA protein (E343K) that significantly alters the interaction between RecA and RecX proteins.
Highlights
The RecX protein is a potent inhibitor of RecA activities
We conclude that RecX protein interacts most effectively with a RecA functional state designated Ao and that the RecA C terminus has a role in modulating the interaction
We previously showed that when RecX protein was added to RecA filaments assembled on circular single-stranded DNA (ssDNA), a slow decline in ATP hydrolysis was observed that reflected a net end-dependent disassembly of the filaments [20] and occurred over a time span of 15–20 min
Summary
The RecX protein is a potent inhibitor of RecA activities. We identified several factors that affect RecX-RecA interaction. The RecA protein promotes a series of DNA pairing and strand exchange reactions that are thought to mimic the function of this protein in vivo [6, 7]. The RecX protein is an inhibitor of RecA function both in vivo and in vitro [19]. Evidence has been obtained that RecX protein acts to cap the growing end of a RecA filament [20]. This activity would serve to limit the length of RecA filaments formed in vivo, and we have proposed that this is the major mode of action of RecX [20]
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