Two-component sensor protein CpxA, periplasmic domain
CpxA_peri is the periplasmic domain-family of the Gram-negative Gammaproteobacteria two-component signalling system, Cpx. It represents the recognition-site for sensing specific envelope stress signals. The fold that the domain-core of CpxA_peri conforms to is a PAS fold. The domain senses the environmental change and triggers a signal transduction to the cytoplasmic domain. As well as the PAS-core, there is a C-terminal tail that is necessary for ligand-sensing and binding to CpxP, a CpxA-associated and a regulatory protein.