Topological analysis of Hin-catalysed DNA recombination in vivo and in vitro.

In vitro studies have demonstrated that Hin-catalysed site-specific DNA inversion occurs within a tripartite invertasome complex assembled at a branch on a supercoiled DNA molecule. Multiple DNA exchanges within a recombination complex (processive recombination) have been found to occur with particular substrates or reaction conditions. To investigate the mechanistic properties of the Hin recombination reaction in vivo, we have analysed the topology of recombination products generated by Hin catalysis in growing cells.

Subunit exchange and the role of dimer flexibility in DNA binding by the Fis protein.

Fis is an abundant bacterial DNA binding protein that functions in many different reactions. We show here that Fis subunits rapidly exchange between dimers in solution by disulfide cross-linking mixtures of Fis mutants with different electrophoretic mobilities and by monitoring energy transfer between fluorescently labeled Fis subunits upon heterodimer formation. The effects of detergents and salt concentrations on subunit exchange imply that the dimer is predominantly stabilized by hydrophobic forces, consistent with the X-ray crystal structures.