An anti-sigma factor for extracytoplasmic function (ECF) sigma factor SigL. ECF sigma factors are held in an inactive form by an anti-sigma factor until released by regulated intramembrane proteolysis (RIP). RIP occurs when an extracytoplasmic signal triggers a concerted proteolytic cascade to transmit information and elicit cellular responses. The membrane-spanning regulatory substrate protein is first cut extracytoplasmically (site-1 protease, S1P), then within the membrane itself (site-2 protease, S2P, Rip1), while cytoplasmic proteases finish degrading the regulatory protein, liberating the sigma factor. Binds 1 Zn(2+) ion per subunit. Interacts with ECF RNA polymerase sigma factor SigL; this should inhibit the interaction of SigL with the RNA polymerase catalytic core. Constitutively expressed from a very weak SigL-independent promoter during growth in culture. Also weakly autoregulated. Forms an operon with sigL. The cytosolic domain interacts with sigma factor SigL. In a double sigL-rslA disruption mutant, no visible phenotype; not more susceptible than the parental strain to several oxidative and nitrosative stresses. Infected DBA/2 mice showed a significantly prolonged survival time relative to mice infected with wild-type bacteria, although bacteria proliferate normally. Belongs to the zinc-associated anti-sigma factor (ZAS) superfamily.