Translocase of the Outer Mitochondrial Membrane: X-ray Structure Determination of Core Components

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This research will address the issue of protein transport into mitochondria, cellular organelles bounded by a complex double-membrane system that are primarily responsible for servicing the energy requirements of actively respiring cells. The outer membrane, or envelope, surrounding each mitrochondrion, is separated from a second (or inner) membrane by an inter-membrane space. The translocase of the outer mitochondrial membrane (TOM) cooperates with the translocase of the inner mitochondrial membrane (TIM) to mediate the passage of unfolded preproteins into the mitochondria. Proteins are usually bulky in their active folded state, so preproteins transit the membrane as extended polypeptide chains, as the channel through which they pass is relatively narrow. Ancillary praoteins aid in recognition and targeting of preproteins, and help to maintain them in an unfolded state prior to their translocation through the pore, and later ensure that they are able to fold into the correct conformation once they have arrived in the mitochondria. Our research will entail determination of the three-dimensional atomic-level structures of selected constituents of the TOM machinery, allowing us to visualise freeze-frame snapshots of some aspects of protein translocation in molecular details. In combination with recent biochemical data, this information will provide an architectural framework which we can use to help in our interpretation of complicated structure-function relationships between components of TOM and other proteins with which they integrate their activities during translocation events. Ultimately such fundamental research will lead to the development of strategies for dealing with disorders linked to mitochondrial defects in humans, including, amongst others, Parkinson's and Alzheimer's diseases.