ExbB
ExbB is essential for TonB-dependent energy transduction as the absence of ExbB prevents TonB responding to the proton motive force, as well as the change of the high-affinity association of TonB for the outer membrane to the cytoplasmic membrane. [1]
ExbB can exist in the TonB system either in a complex with ExbD (to a ratio of 3.5:1) or on its own (where no ExbD is present), which has been suggested to play a role in the diverse roles of TonB. [1]
StructureStructure
ExbB consists of three transmembrane domains, with two large portions of the protein representing the majority of the protein in the cytoplasm and two smaller portions in the periplasm.