Chemistry Colloquium - Susan Buchanan, Ph.D. NIH

Structural insight into the role of the Ton complex in energy transduction

January 18, 2018
10:30 am - 11:30 am
Location
006 Steele
Sponsored by
Chemistry Department
Audience
Public
More information
Phyllis Ford

In Gram-negative bacteria, outer membrane (OM) transporters import nutrients by coupling to an inner membrane (IM) protein complex called the Ton complex. The Ton complex consists of TonB, ExbB, and ExbD, and uses the proton motive force (pmf) at the IM to transduce energy to the OM via TonB. The mechanism and stoichiometry of the complex have remained unknown. Here, we structurally characterize the Ton subcomplex (ExbB/ExbD) from E. coli using X-ray crystallography, electron microscopy, DEER spectroscopy, and crosslinking, revealing that ExbB assembles as a pentamer containing a transmembrane pore filled by a single ExbD that is dimerized to a second ExbD sitting outside of the pore. Combined with our studies using the fully assembled Ton complex, we report a stoichiometry consisting of a pentamer of ExbB, a dimer of ExbD, and at least one TonB. Electrophysiology studies show that the Ton subcomplex forms pH-sensitive cation-selective channels, providing insight to the mechanism by which it may harness the pmf for energy production.

 

Location
006 Steele
Sponsored by
Chemistry Department
Audience
Public
More information
Phyllis Ford