For nearly six decades, chemotaxis - a ubiquitous biological behaviour enabling the movement of a cell or organism toward or away from chemicals -has served as a paradigmatic model for the study of cellular sensory signal transduction and motile behavior. The relatively simple chemotaxis machinery of E. coli is the best understood signal transduction system and serves as a powerful tool for investigating the molecular mechanisms that proteins use to detect, process, and transmit signals. The sensory apparatus of E. coli cells is an ordered array of hundreds of basic core signalling units consisting of three essential components, the transmembrane chemoreceptors, the histidine kinase, and the adaptor protein. The core units further assemble into a two-dimensional lattice array which allows cells to amplify and integrate many varied and possibly conflicting signals to locate optimal growing conditions. To understand the underlying molecular mechanisms of chemosensory array assembly, activation and high cooperativity, it is essential to determine the precise interactions between the core signalling components in the context of the array. We propose to use a combination of cutting-edge cryoET structural methods and multi-scale molecular simulations, as well as in vivo functional assays, to investigate the structural and dynamical mechanisms underlying signal transduction and regulation. The research plan is divided into three aims: 1. Determine the structural basis of signal transduction and array cooperativity 2. Define conformational states and dynamics of the array 3. Obtain time-resolved structural snapshots of signalling pathway Our results will establish, in atomistic detail, the chemotaxis signalling pathway that is shared by diverse chemotactic species, including a wide-range of human and plant pathogens, thus impact on multiple disciplines, from antimicrobial drug development to understanding responses to hormones and neurotransmitters in eukaryotic cells.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Establishing the atomic arrangements in a molecule or a solid has been feasible for about 100 years by X-ray diffraction; most "pictures (stills)" of the structure of, for example, salt, insulin, haemoglobin and foot and mouse disease virus are based on this technique of scattering X-ray from crystals. For less ordered materials, like glasses and liquid solutions, partial, local structures can be derived from X-ray absorption spectroscopy. Both techniques require scattering off electrons and thus tell us about the atomic arrangements and some insight into electronic distributions. Chemical and light-induced changes are movements of electrons and atoms to new sites and so visualizing these evolutions by X-ray methods can provide chemical videos of reactions which have greater richness than before and after stills; this is the molecular parallel of picturing a galloping horse. Generally changes on the timescales of atomic motion occur between a 1/100 and 1 picosecond (1 ps = 1 millionth of a microsecond), and this has been monitored by changes in the uv and visible spectrum (colour). This provides little information about structure. Infra-red spectroscopy can be used for timescales greater than 1 ps, and is characteristic of functional groups within molecules. This proposal provides a means of approaching the detail of a molecular "still" through chemical changes. The Diamond Light Source is the brightest X-ray source in the UK, and provides the opportunity of studying structures on a timescale of 10s of picoseconds. This is fast enough to catch many excited states of fluorescent materials, and to observe the reactions of the most reactive of transient molecules. UV-visible and infrared spectroscopies will be monitored after changes induced by a laser pulse of about 1/5 of a picosecond. The fast laser spectroscopy will be combined with the rapidly developing technique of photocrystallography, where it is possible to obtain full 3-D solid-state structures of photoactivated species that have lifetimes in the nanosecond to millisecond range, so that it will be possible to make "molecular movies" showing how key chemical and biological processes occur. Thus, it will be possible to study important catalytic, sensor and non-linear materials across the time scales from picoseconds to milliseconds, to see how properties and functions develop over time. Sampling procedures for crystals, solutions and films will be developed and made available to other research groups. The whole approach should transform the way we think about chemical reactions. From such an approach there will be a fraction of problems for which even faster measurements would be fascinating. In recent years laser light in the X-ray region has become available in the USA and Japan (by X-ray free electron lasers, XFELs), and sources are being built in Europe (Germany and Switzerland). They provide an X-ray pulse of about 1/50 of a picosecond, faster than most molecular vibrations, and thus the X-ray movie of a chemical reaction is feasible. This proposal will provide a test-bed for researchers in the chemical sciences to develop their technique for visualizing their reactions. The facility will be based on the Harwell site adjacent to the equipment and expertise of the Diamond Light Source and Central Laser Facility, both of which are user facilities of the highest rank.

See Je-S application of Oxford University (lead applicant, joint reference P1936803)

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.