Combining low resolution, high resolution, functional, and simulation techniques : In the study of pentameric ligand-gated ion channels

Sammanfattning: Combining methods yielding different information is a powerful approach for understanding structural biology in general, and in particular systems such as pentameric ligand-gated ion channels (pLGICs). Pentameric ligand-gated ion channels are membrane proteins that sense chemical signals, which they convert to changes in membrane potential. pLGICs constitute important drug targets in humans, for example as sites of action for general anaesthetics. There are bacterial homologs, of which some - like the Gloeobacter violaceus ligand-gated channel GLIC - are suitable model systems, while others - like DeCLIC from a Desulfofustis deltaproteobacterium - demonstrate the structural range of this protein family.This thesis presents how low resolution, high resolution, functional, and simulation techniques have been combined in the study of GLIC and DeCLIC. The methods covered are small-angle neutron scattering (low resolution structural method), cryogenic electron microscopy (high resolution structural method), electrophysiology (functional method), and molecular dynamics simulations (simulation method), with a particular focus on the scattering and simulation experiments. In the presented work, simulations and functional experiments are combined to elucidate modulation of GLIC by general anaesthetics, the average solution structure of both GLIC and DeCLIC is described from small-angle scattering utilizing conformational sampling from simulations, and new conformations of DeCLIC are found through cryogenic electron microscopy - including an open conformation consistent with scattering under corresponding solution conditions.This work has contributed to both the understanding of complex allosteric modulation, and of the conformational range available to pentameric ligand-gated ion channels. On the methodological side, I have furthered approaches for integrating small-angle neutron scattering and molecular dynamics simulations to describe membrane protein structure in solution - which stands to increase the information gained from scattering experiments, and to promote the use of scattering as a complementary technique in structural studies.