Mechanism of energy transduction to the outer membrane of escherichia coli

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The research programme of our laboratory is concerned with the structure and function of the double membrane envelope, or cell wall, of a large group of bacteria called the Gram negatives.  Our research deals with interactions between the inner and outer membrane in the transport of materials across the outer membrane, as well as the physiology and regulation of extracytoplasmic stress responses that are involved in maintaining the structure and proper functioning of the double membrane envelope.      In our current research, we are studying the structure and mechanism of action of a protein complex that allows Gram negative bacteria to import essential nutrients.  The TonB/ExbB/ExbD complex in Escherichia coli is used to transport iron atoms into the cell for use in a wide variety of cellular processes.  The bacteria use highly specific transport mechanisms to capture iron, first by binding it to siderophores and then by binding the siderophores to high affinity receptors in the outer membrane and transporting them into the cell. It requires energy to accomplish this transport across the outer membrane, and the TonB complex "transduces" this energy from the inner to the outer membrane.  In our experimental studies we are using specific fragments of TonB to test fundamental hypotheses about the mechanism by which the TonB/ExbB/ExbD complex provides energy from the inner membrane for the transport of siderophores across the outer membrane.        We have also recently demonstrated a link between a very large group of coordinately regulated genes involved in the energy balance of the cell (the catabolite repression regulon) and the regulation of two other groups of genes whose function is to maintain the double membrane envelope in a healthy state (the extracytoplasmic stress regulons).  In our current studies we are also determining the nature of the links between these two important groups of genes more precisely.