Structural and Functional Studies of Small Membrane Proteins

Recent biomedical advances including anti-viral and anti-cancer immunotherapies, and structure-based drug design are driven by insights from structural biology. Despite notable structure-based successes, membrane proteins remain difficult targets and consequently a significant challenge. Membrane protein targets are comparatively high-risk, expensive and require significant optimisation for success. The Membrane Protein Laboratory was established to ensure that membrane protein structural biology was more accessible by combining recently developed high-throughput technologies for protein production, crystallisation and cryoelectron microscopy with the data collection systems at Diamond Light Source. We have welcomed well over 250 visiting scientists to our facility and supported research that has led to at least one atomic resolution membrane protein structure a year since 2012.

Membrane proteins are found at the junctions between the outside world and the inner workings of the cell. Multicellular organisms such as humans use membrane proteins for communication, to acquire nutrients and detect threats. More than half of all medicines alter membrane protein function. It is important to link structure to function, but when we remove membrane proteins from their membranes in order to study them, we lose their native lipid–based environment which can drastically affect membrane protein function. Reconstitution into liposomes (essentially balls of lipids), allows us to mimic membranes and restore function. We can additionally define the lipid content, enabling the effect of different lipids on structure and function to be studied.

Using our high-throughput protein production platform we have identified ideal conditions for working with a number of medically relevant prokaryotic and eukaryotic membrane proteins but lack the ability to quickly and efficiently characterise these proteins in native-like conditions. Working closely with research groups across the life-science division at Diamond as well as Structural Biology at the Rosalind Franklin Institute (RFI) we plan to expand our high-throughput protein production platform to encompass reconstitution of membrane proteins into proteoliposomes (protein in the liposome). We will screen different lipid combinations and ratios to understand their effect on the function of selected membrane proteins. Optimised proteoliposomes will be structurally characterised using techniques such as analytical ultra centrifugation and small-angle X-ray scattering prior to high-resolution structural studies using single-particle cryoelectron microscopy. We will also work with highly-specific nanobodies (small llama derived antibodies) to help us to localise targets during imaging as well as study the proteins functionally.