Protein-protein interfaces in chemotaxis receptor complexes and their role in signaling.

Chemotaxis receptor complexes sense chemical gradient in the cellular environment to direct swimming towards favorable environments. The core signaling units of these complexes are made up of two trimers-of-dimers of chemoreceptors, two CheW and a CheA dimer, which further assemble into large hexagonal signaling arrays. Structural and biochemical studies have provided important information on the architecture and interfaces of these complexes. However, the signaling pathway of these complexes that controls the kinase is not fully understood. In this review, we highlight the highest resolution models of this system and examine the current consensus on the protein-protein interfaces based on models and interface experiments. We also highlight differences observed between signaling states for the individual proteins and the protein interfaces that are proposed to be part of the signaling mechanism. Overall, we conclude that there is strong structural consensus for the protein interfaces but, despite some intriguing results, more information is needed to understand how the interfaces change between signaling states and the role they play in signaling. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at https://proteopedia.org/w/Journal:FEMS_Microbiology_Reviews:1.