Excision of the Shigella resistance locus pathogenicity island in Shigella flexneri is stimulated by a member of a new subgroup of recombination directionality factors.

Pathogenicity islands are capable of excision and insertion within bacterial chromosomes. We describe a protein, Rox, that stimulates excision of the Shigella resistance locus pathogenicity island in Shigella flexneri. Sequence analysis suggests that Rox belongs to a new subfamily of recombination directionality factors, which includes proteins from P4, enterohemorrhagic Escherichia coli, and Yersinia pestis.