Sigma factors are initiation factors that promote the attachment of RNA polymerase (RNAP) to specific initiation sites and are then released. Extracytoplasmic function (ECF) sigma-E controls the envelope stress response, responding to periplasmic protein stress, increased levels of periplasmic lipopolysaccharide (LPS) as well as heat shock and oxidative stress; it controls protein processing in the extracytoplasmic compartment (By similarity). ECF sigma-E is held in an inactive form by its cognate anti-sigma factor (RseA) until released by regulated intramembrane proteolysis (RIP). RIP occurs when an extracytoplasmic signal (periplasmic stress and excess LPS) triggers a concerted proteolytic cascade to transmit information and elicit cellular responses. The anti-sigma factor RseA is an inner membrane protein, binding sigma-E in the cytoplasm and RseB in the periplasm. RseA is first cut extracytoplasmically (site-1 protease, S1P, by DegS), then within the membrane itself (site-2 protease, S2P, by RseP), while cytoplasmic proteases (predominantly ClpX-ClpP) finish degrading the regulatory protein, liberating sigma-E. Degradation of RseA requires 2 signals to activate DegS; an outer membrane protein (OMP) signal activates DegS, while an LPS signal causes release of RseB from RseA, freeing RseA to be cleaved (By similarity). Interacts transiently with the RNAP catalytic core formed by RpoA, RpoB, RpoC and RpoZ (2 alpha, 1 beta, 1 beta' and 1 omega subunit) to form the RNAP holoenzyme that can initiate transcription. Interacts 1:1 with anti-sigma-E factor RseA which prevents binding to RNAP catalytic core (By similarity). Associates with the inner membrane via RseA. The sigma-70 factor domain-2 mediates sequence-specific interaction with the -10 element in promoter DNA, and plays an important role in melting the double-stranded DNA and the formation of the transcription bubble. The sigma-70 factor domain-2 mediates interaction with the RNA polymerase subunits RpoB and RpoC (By similarity). The sigma-70 factor domain-4 contains a helix-turn-helix (H-T-H) motif that mediates interaction with the -35 element in promoter DNA. The domain also mediates interaction with the RNA polymerase subunit RpoA. Interactions between sigma-70 factor domain-4 and anti-sigma factors prevents interaction of sigma factors with the RNA polymerase catalytic core (By similarity). Belongs to the sigma-70 factor family. ECF subfamily.