Integrating theory and experiments to study complex protein dynamics at the surface of lipid membranes

The cellular membrane is a complex biophysical environment that occupies a central position in many fundamental biological processes. In association with the membrane there are a wide variety of proteins, macromolecular actors with crucial roles in driving those processes. Being a primary point of contact between the inside and outside of cells, membrane proteins are targeted by the majority of approved therapeutic drugs. New methods that can unveil the mechanisms by which these molecules function are therefore crucial in deepening our biomolecular understanding and can provide rational approaches for the design of novel therapeutic approaches. Conformational dynamics are an important factor in driving the behaviour of membrane proteins. Receptors, channels and other membrane-embedded proteins function by populating distinct structural states and interconverting between them. However, the molecular detail of these heterogeneous processes is extremely challenging to elucidate with the current analytical tools, generally tailored for homogeneous protein states. This thesis focuses on the methodological development of approaches to accurately characterise the dynamical behaviour of membrane proteins. The methods outlined combine the use of experiments and theoretical sampling to generate ensemble descriptions of membrane proteins. Specifically, the experimentally-restrained molecular dynamics approach is further developed for the incorporation of solid-state NMR observables. The accuracy of this method is validated in the context of membrane proteins and subsequently applied to the study of three different biological systems: the cardiac regulatory protein phospholamban, the influenza proton channel M2 and the G-protein coupled receptor CXCR1. The generated ensembles reveal some important conformational transitions in these membrane proteins, and highlight the importance of combining theory and experiments in order to achieve an accurate, detailed description of biomolecular dynamics in lipid membranes.Open Acces