In Gram-negative bacteria, envelope stress signals such as unfolded outer membrane proteins (OMP) activate the periplasmic protease DegS. This protease then triggers a cellular pathway to alleviate the stress. Now Sohn et al. (2007) show conclusively that inhibition of DegS is relieved allosterically by binding of the C-terminal sequences in unfolded OMPs to the PDZ domain of DegS.
