The Role of Acidic Residues and the Electrochemical Potential in Membrane Protein Assembly

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9728344 Dalbey Lay Abstract A fundamental process in cell biology is the way in which proteins are inserted into cellular membranes and achieve their distinctive and unique topology within the membrane. This project is based on studies of bacteria in this laboratory and the discovery that negatively charged residues within certain bacterial membrane proteins play an active role in membrane insertion. This insertion apparently requires only the energy of the electrochemical gradient across the membrane. The hypothesis is that the electrochemical gradient promotes insertion by the direct driving force of the membrane potential on the negatively charged amino acids in the specific regions of the membrane protein that will be translocated. This is in contrast to other mechanisms of insertion in other systems in which insertion of specific proteins requires a complex set of additional proteins that must recognize and interact with the translocated protein. The novel hypothesis will be tested by examining the insertion of a variety of bacterial proteins and hybrid protein constructs that are mutated at specific residues thought to play a role in translocation. The membrane pH and potential will be changed to assess the role of these factors on transport. This research on the mechanism of insertion into bacterial membranes will likely be fundamentally important in the understanding of similar processes in mitochondria of eukaryotic cells since these cell organelles are believed to be evolutionarily derived from symbiotic bacteria. ***