Hexameric and pentameric complexes of the ExbBD energizer in the Ton system.

ABSTRACT: Gram-negative bacteria import essential nutrients such as iron and vitamin B₁₂ through outer membrane receptors. This process utilizes proton motive force harvested by the Ton system made up of three inner membrane proteins, ExbB, ExbD and TonB. ExbB and ExbD form the proton channel that energizes uptake through TonB. Recently, crystal structures suggest that the ExbB pentamer is the scaffold. Here, we present structures of hexameric complexes of ExbB and ExbD revealed by X-ray crystallography and single particle cryo-EM. Image analysis shows that hexameric and pentameric complexes coexist, with the proportion of hexamer increasing with pH. Channel current measurement and 2D crystallography support the existence and transition of the two oligomeric states in membranes. The hexam

SUBMITTER: Maki-Yonekura S 

PROVIDER: S-EPMC5903867 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature