Research Fellows Directory
Dr Ian Collinson
University of Bristol
All living cells are enveloped by a thin film made up of molecules called phospholipids. This skin-like layer, or ‘membrane,’ separates the outside of the cell from the living biochemical reactions occurring inside. In the case of more complicated cells, such as those found in humans, these membranes also compartmentalise the cell forming organelles with specialised functions. The human genome contains about 20,000 genes; nearly a third encode proteins that reside in membranes. Membrane proteins function to overcome the barrier formed by the membrane itself and to facilitate the essential exchange of information, nutrients, waste products, and transport of larger molecules (like other proteins) between the environment and the cell interior.
Cells have a large demand for protein transport, either for secretion out of the cell, import into specialised organelles like mitochondria and chloroplasts, as well as for the incorporation of proteins into membranes. A number of specific systems have evolved to enable such transport. One of them, the so-called ‘Sec system,’ is responsible for the majority of protein secretion and membrane insertion in every cell in every organism. Therefore, it is crucial that we understand how this conserved and fundamental biological process works. This proposal seeks to resolve this outstanding problem through an analysis of the structure and biochemical properties of the functionally reconstituted machinery. We have produced the complex capable of both protein secretion and membrane protein insertion - the so-called holo-translocon (HTL). So far, we have established conditions in which we can reconstitute the complex in the natural environment of the membrane. This has provided the important ground-work to analyse the architecture and biochemical properties of the machinery, to help us understand how it works in molecular detail. The results of this work will assist in our basic understanding of a conserved and fundamental process.
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