The general stress response sigma factor in alphaproteobacteria, sigma EcfG is inactivated by the anti-sigma factor NepR, which is itself regulated by the response regulator PhyR. NepR forms two helices that extend over the surface of the PhyR subdomains. Homology modeling and comparative analysis of NepR, PhyR and sigmaEcfG mutants indicate that NepR contacts both proteins with the same determinants, showing sigma factor mimicry at the atomic level. This entry represents NepR domains found in alphaproteobacteria [1].

1: Structural basis for sigma factor mimicry in the general stress response of Alphaproteobacteria. Campagne S, Damberger FF, Kaczmarczyk A, Francez-Charlot A, Allain FH, Vorholt JA; Proc Natl Acad Sci U S A. 2012;109:E1405-E1414. PMID:22550171