Exploring magnetically aligned bilayers as a novel tool for membrane protein crystallisation

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Membrane-embedded proteins (or membrane proteins) are amongst the most influential for the survival, correct behaviour and function of cells. They form the means by which cells interact with their environments, by which they import nutrients and expel potentially poisonous molecules, and communicate with each other. In humans, membrane proteins comprise almost a third of all known proteins, and over half of the currently available drugs act on membrane proteins. Thus, studying the roles of membrane proteins and how they function is a pursuit shared by both academic research scientists and the pharmaceutical industry alike.A powerful means for studying the role and function of proteins is visualising their three-dimensional shape with enough detail to distinguish individual chemical groups and atoms. Such analysis allows us to understand the purpose of each protein component as if we were observing a machine, and to envision ways of assisting or disrupting its mechanism that can then be translated into drugs and therapies for diseases. X-ray crystallography is the premier method by which we visualise proteins at this level of detail; however, this method requires the formation of highly ordered crystals where protein molecules pack against each other in a predictable and regular manner. Due to the fact that membrane proteins need to be extracted from their natural membrane environment in order to be crystallised, they are often damaged and therefore they do not easily form crystals. It is for this reason that, despite their enormous importance in living organisms, membrane proteins make up a very small proportion, less than 2%, of proteins for which the detailed shape is known. Thus, developing novel tools that induce membrane proteins to form crystals could tremendously expand our detailed understanding of cellular mechanisms.Traditionally, membrane proteins were isolated and handled in the presence of soap-like detergent molecules; however, such detergents make the proteins less likely to function correctly or to form crystals. For this reason, researchers have been developing advanced methods that provide a more membrane-like environment for the proteins during crystallisation, e.g. by the addition of lipids that are similar to those in the cell membrane. When membrane proteins do crystallise through these methods the crystals often consist of spontaneously formed stacks of lipid bilayers, an arrangement that vaguely resembles the situation the protein would encounter in the membrane of a living cell. In this proposal we aim to develop a new method that assists the regular packing of membrane proteins in such stacked lipid bilayers, and thereby increases the probability that they form crystals. To do so we will utilise strong superconducting magnets, which are known to impose order in membranes by forcing their orientation to follow the direction of the magnetic field. We hypothesise that in this way membrane-embedded proteins will also be forced toward a particular direction, and this spatial restriction may induce them to pack more readily into crystals. Should this magnetic alignment crystallisation ('MAX') approach prove successful, we aim to further develop the use of magnets in the crystallisation of membrane proteins into a tool widely available in the academic community and industry.