Abstract 2895 Structural Characterization of TonB Proteins in Bacteroides thetaiotaomicron

Microorganisms break down starch and other complex carbohydrates in the human gut.In Bacteroides thetaiotaomicron (B.theta), starch binds to outer membrane lipoproteins to initiate transport.The associated transmembrane TonBdependent transporter (TBDT) features a highly conserved sequence called the Ton Box, which interacts with the Cterminus of the TonB protein to open the TBDT channel, allowing starch to enter the cell.This C-terminus domain is known to interact with the TBDT, but the structure of this domain and the mechanism of this interaction are not yet known.B. theta encodes 11 distinct TonB homologs, of which several have high sequence similarity with TonB-like proteins of related Bacteroides species.The goal of this work is to purify TonB proteins using nickel affinity chromatography and fast protein liquid chromatography, and to obtain crystals of each protein.This will allow us to determine their structure via xray crystallography and understand the mechanism by which they interact with the transport protein.TonB3 and TonB7 were successfully overexpressed in E. coli and sufficiently purified.Initial crystallization screens for TonB3 produced several promising crystals.Future work involves crystallization screening of TonB7 and optimization of TonB3 crystals, and structural determination of both proteins using x-ray crystallography.