Determinants of a Cytoplasmic Membrane Energy Transduction System

Bowling Green State University, Bowling Green OH

Investigators

Abstract

The TonB and TolA systems of Gram-negative bacteria represent a unique set of proteins that harvest the potential energy of the cytoplasmic membrane electrochemical gradient, package it, and deliver it to a distant location. These systems support the efficient harvesting of the essential nutrient iron (via TonB) and maintain the integrity of the principle bacterial defensive barrier - the outer membrane (via TolA). This project focuses on how energy is harvested and packaged. In particular, the approach exploits the ability of certain components from one system to function in the other system. Because this molecular "cross-talk" is imperfect, it provides a means to identify the common features that harvest energy and to distinguish unique features through which energy is transmitted. By mixing and matching specific sections of these proteins and evaluating the function and efficiency of such chimeras, this study will identify the specific interactions that mediate energy acquisition and transmission. The mechanisms for this type of energy transduction are of fundamental importance in biological systems, and dissection of the problem at the molecular level may establish far-reaching paradigms. The current work emphasizes the harvest and packaging aspect of these systems, with an added benefit of establishing a foundation for examining the delivery function of the system. This is particularly important for the TolA system, the study of which has suffered from the lack of adequate tools. From a practical standpoint, the outer membrane is a crucial structure - forming the principle interface between bacterium and environment. How this structure is energized is relevant to disciplines ranging from environmental sciences to pathogenesis. As systems that energize this defensive barrier, the TonB and TolA systems present novel potential targets for therapeutic agents, and may prove of consequence in biotechnology settings where transport across this barrier is an issue. The project will involve training graduate and undergraduate students