Bacillus subtilis LrpC is a sequence-independent DNA-binding and DNA-bending protein which bridges DNA

Genetic evidence suggests that the Bacillus subtilis lrpC gene product participates in cell growth and sporulation. The purified LrpC protein, which has a predicted molecular mass of 16.4 kDa, is a tetramer in solution. LrpC binds with higher affinity (K(app) ~ 80 nM) to intrinsically curved DNA than to non-curved DNA (K(app) ~ 700 nM). DNase I footprinting and the supercoiling of relaxed circular plasmid DNA in the presence of topoisomerase I revealed that LrpC induces DNA bending and constrains DNA supercoils in vitro. The LrpC protein cooperatively increases DNA binding of the bona fide DNA-binding and DNA-bending protein Hbsu. LrpC forms inter- and intramolecular bridges on linear and supercoiled DNA molecules, resulting in a large network and DNA compactation. Collectively, these findings suggest that LrpC is an architectural protein and that its activities could provide a means to modulate DNA transactions.