PAS domains in bacterial signal transduction

[Display omitted] •PAS domains are common sensing, signaling, dimerization, and localization domains.•Sensing versatility derives from a conserved cleft that binds cofactors and ligands.•PAS signaling involves repositioning of the PAS β-sheet and adjoining helices.•PAS connects to diverse effector domains to regulate distinct cellular functions.•PAS-effector domain structures have begun to clarify protein signaling mechanisms. PAS domains are widespread, versatile domains found in proteins from all kingdoms of life. The PAS fold is composed of an antiparallel β-sheet with several flanking α-helices, and contains a conserved cleft for cofactor or ligand binding. The last few years have seen a prodigious increase in identified PAS domains and resolved PAS structures, including structures with effector and other domains. New bacterial PAS ligands have been discovered, and structure-function studies have improved our understanding of PAS signaling mechanisms. The list of bacterial PAS functions has now expanded to include roles in signal sensing, modulation, transduction, dimerization, protein interaction, and cellular localization.