The influence of metal fluorides on the structure and dynamics of phosphoryl transfer enzymes

点击翻译按钮获取中文摘要

Living systems depend on enzymes to speed up a multitude of chemical reactions via catalysis. One of the most widespread reactions required involves the transfer of a phosphate group between different molecules - phosphate transfer reactions play a central role in, for example, providing energy to cells, the synthesis and breakdown of vital components, and communication systems within cells. Phosphate groups are extremely difficult to remove and so highly efficient catalysis is crucial for the control of these cellular processes. Although model studies have taught us much about the intrinsic chemistry required, our understanding of the origins of the enormous accelerations of reaction rates afforded by phophate transfer enzymes - from taking longer than the time for which the universe has been in existence to less than a second - are at a rudimentary level . Ideally, we would study a snapshot of an enzyme at the critical point of catalysis but this is unachievable since the lifetime of such species is too short. Hence, the current framework for understanding of how this catalysis occurs depends on studies involving chemicals that look like the species present at the critical point of catalysis but which trap the enzyme in this state. We have discovered that a phosphate transfer enzyme is capable of assembling magnesium fluoride in the site where catalysis occurs. Magnesium fluoride looks more similar to the species predicited to be the determinant of the catalytic rate than any other yet described, but is not normally observable in the absence of the enzyme. The enzyme is using its immense binding capabilities to stabilise magnesium fluoride. This provides us with strong evidence as to how the enzyme is catalysing the phosphate transfer reaction. We will compare how the protein behaves in terms of its structure and movement in the presence of magnesium fluoride compared with the previously best known analogue of phosphate transfer catalysis, aluminium fluoride. The triangular shape of the magnesium species fits far closer to the transfering phosphate group than the square aluminium species. We will also investigate whether previously reported triangular aluminium species are in fact magnesium species, and we will examine the different ways in which fluoride can bind to the enzyme. The conclusions should be broadly applicable to other phosphate transfer enzymes. An understanding of this process is vital to the design inhibitors of enzymes for use as therapeutic agents (drugs) and to technologies that use enzymes out of their biological context, for example bioremediation. It will also help the theoretical understanding of how important biological molecules work.