Title: Structures of macromolecular assemblies
Funder: Medical Research Council

Abstract: Mitochondrial ATP synthase (also known as F1Fo-ATPase) is the enzyme responsible for the synthesis of the vast majority of cellular ATP. It is powered by a trans-membrane proton motive force that is established by the oxidation of nutrients. The enzyme consists of two domains: a globular water-soluble catalytic domain (F1) that contains the active sites and a trans-membrane domain (Fo) that contains a proton channel. These domains are linked by a central stalk (which is part of F1) and a peripheral stalk. Catalysis proceeds by a rotary mechanism, in which the central stalk of F1 and a ring of subunits in Fo rotate as an ensemble, driven by proton translocation through Fo, while the peripheral stalk acts as a stator. The rotation of the asymmetric central stalk produces conformational changes at the catalytic sites in F1 that promote substrate binding, ATP synthesis and product release. The F1 domain in isolation hydrolyses ATP, which generates a rotation of the central stalk. Protein crystallography is being used to study the structure of ATP synthase, F1-ATPase and other components of the ATP synthase in order to understand the catalytic mechanism and the molecular basis for the generation of rotation. The structures of metallo-fluoride inhibited complexes have provided significant insights into catalysis, while more recently the structures of several components of the peripheral stalk have been determined, both in isolation and bound to F1. The majority of the work has been carried out on the bovine mitochondrial enzyme, but the enzyme from the yeast Saccharomyces cereviseae is also being studied, and the structure of F1-ATPase from a thermo-alkaliphilic Bacillus has also been solved at 3Å resolution. In a recent breakthrough, the entire ATP synthase from a bacterial source has been crystallised and the structure has been determined at 4Å resolution. This has provided the first structural information on the proton pathway in the Fo segment. Integral membrane proteins play a wide variety of crucial roles in living cells including signalling and transport. G-protein coupled receptors (GPCRs) are the largest family of membrane proteins in the human genome, and are involved in the regulation of many key physiological functions. For this reason, they are the targets of a wide range of pharmaceutical products. Crystallographic studies of GPCRs are aimed at understanding how ligand binding modulates their activity and the basis of ligand selectivity. The structure of beta1 adrenergic receptor has been determined with a variety of bound agonists and antagonists, and the structure of the adenosine A2a receptor has given insights into the conformational changes that occur on activation. Most recently, the structure of a GPCR in complex with an engineered ras domain of its cognate G protein has been determined. This structure gives important insights into the mode of interaction of the GPCR with the G protein. The MOSFLM program for processing X-ray diffraction data is undergoing continuous development. This includes a completely new graphical user interface (iMosflm), for ease of use by inexperienced users. Recent developments have allowed processing diffraction images when multiple lattices are present, although further work is required to optimise this procedure.


Research activity codes: 1.1 NORMAL BIOLOGICAL DEVELOPMENT AND FUNCTIONING;1.4 METHODOLOGIES AND MEASUREMENTS;2.2 FACTORS RELATING TO PHYSICAL ENVIRONMENT
Health categories: GENERIC HEALTH RELEVANCE;INFECTION