Metal fluorides - multi-functional tools for the study of phosphoryl transfer enzymes

Enzymes facilitating the transfer of phosphate groups constitute the most extensive protein group across all kingdoms of life, making up approximately 10% of the proteins found in the human genome. Understanding the mechanisms by which enzymes catalyse these reactions is essential in characterising the processes they regulate. Metal fluorides can be used as multifunctional tools for the study of these enzymes. These ionic species bear the same charge as phosphate and the transferring phosphoryl group and, in addition, allow the enzyme to be trapped in catalytically important states with spectroscopically sensitive atoms interacting directly with active site residues. The ionic nature of these phosphate surrogates also allows their removal and replacement with other analogues. Here, we describe the best practices to obtain these complexes, their use in NMR, X-ray crystallography, cryoEM and SAXS and describe a new metal fluoride, scandium tetrafluoride, which has significant anomalous signal with soft X-rays. Highlights Enzymes that catalyse phosphoryl transfer are the largest family of enzymes and are involved in the storage and transmission of genetic information, energy transfer, signalling and cellular differentiation Metal fluorides form a comprehensive tool kit to study the mechanisms of these enzymes by stabilizing the active conformation; mimicking both the transition state and ground state; and placing spectroscopically sensitive atoms into the active site A guide is presented to the optimal formation of these complexes and their use in a wide variety of techniques in structural biology