The chemical biology of G-proteins

One of the most remarkable features of the chemistry of living organisms is the evolutionary utilisation of phosphate esters to provide biopolymers that encode genetic information, for temporal protein regulation, for the generation and distribution of free energy throughout the cell, and as a ubiquitous handle for metabolic intermediates. The solution to the paradox between the remarkable chemical stability of phosphate esters and their facile manipulation lies in the catalytic power of enzymes to make and break P-O-C and P-O-P bonds rapidly, giving some of the largest enzymatic rate accelerations yet identified. We have made extensive use of metal fluoride complexes of archetypal enzymes to unravel how this remarkable level of catalysis is achieved. These studies have established the dominant role played by charge in catalysis by these enzymes, and it is this element that we intend to expand upon in the proposed study. Using a combination of structural biology and computational chemistry, we will elucidate how small G-proteins and related enzymes achieve catalysis. The study will make extensive use of heteronuclear NMR, and X-ray crystallography, coupled with cutting-edge theory to calculate rigorous atomic charges from first principle electron densities, as well as characterising bonding patterns and non-covalent interactions. The student will also be exposed to the development of a novel force field called QCTFF, which will be trained specifically for phosphate groups. This will enable structural predictions that are not possible with standard ab initio quantum chemistry.