This family is conserved in Enterobacteriaceae. It is one of a series of proteins, expressed by these bacteria in response to stress, that help to regulate Sigma-S, the stationary phase sigma factor of Escherichia coli and Salmonella. IraP is essential for Sigma-S stabilisation in some but not all starvation conditions [1].

1: Multiple pathways for regulation of sigmaS (RpoS) stability in Escherichia coli via the action of multiple anti-adaptors. Bougdour A, Cunning C, Baptiste PJ, Elliott T, Gottesman S; Mol Microbiol. 2008;68:298-313. PMID:18383615