Gating mechanism of a potassium channel (KirBac3.1) studied using high resolution cryo electron crystallography

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Almost every single process in the human body is controlled at some level by electrical signals, from the way our hearts beat, the way our muscles move, to the way we think. These electrical signals are generated and controlled by ion channels which act as electrical 'nano-switches' to control the selective movement of charged ions like potassium (K+) and sodium (Na+) into and out of the cell. As a consequence of this fundamental importance, a large number of genetically inherited diseases or 'channelopathies' are the result of defective ion channel function. These diseases include cystic fibrosis, diabetes, epilepsy and many other rarer diseases of the heart, brain, nerves and kidneys. Ion channels also have considerable potential to be exploited as molecular switches in nanoscale electrical devices and so understanding how they open and close, and how this process is controlled is of considerable interest. Inwardly-rectifying potassium (Kir) channels are expressed in almost every cell of the body and underlie the basic electrical activity which is found in these cells. Structural studies of these human channels is extremely difficult. However, related 'KirBac' channels exist in bacteria and these are much more amenable to biochemical and structural studies. In our preliminary investigations we have expressed and purified KirBac3.1 and shown we are able to obtain images of this channel in both the open and the closed state using a powerful electron microscope. In this proposal we aim to use a new state-of-the-art microscope and mutant KirBac3.1 proteins to improve the resolution of our images we are able to achieve. This will allow us to obtain high-resolution images of the KirBac3.1 channel in both the closed and open states and to address the structural changes which occur as the channel changes shape between the open and closed states. Improving our understanding of how this process occurs at the molecular level will provide a major insight into how related K+ channels open and close and how this process becomes defective in the disease state.