Identification of the Elusive Hydronium Ion Exchanging Roles with a Proton in an Enzyme at Lower pH Values


  • The neutron PCS is funded by the DOE-OBER. A.Y.K. was partly supported by LANL (LDRD grant 20080789PRD3). M.M. and P.L. were partly supported by an NIH-NIGMS-funded consortium (1R01M071939-01) between LANL and LBNL to develop computational tools for neutron protein crystallography. B.L.H. is supported by NSF 446218. V.T.F. and S.A.M. acknowledge support from the EPSRC under grants GR/R47950/01, GR/R99393/01, and EP/C015452/1. The new D19 diffractometer was built as part of a collaboration between Durham University, Keele University, Bath University, and ILL. We gratefully acknowledge the help of John Archer, John Allibon, and the efforts of the ILL detector group.


original image

Visible to neutrons: Although thought to be involved in biological processes, hydronium ions had never been identified in biomacromolecular crystallographic structures. A hydronium ion has now been found by neutron and X-ray crystallography to interchange with metal cofactors in the active site of an enzyme. Under more acidic conditions, the hydronium ion is dehydrated to a proton, and the binding site collapses (see picture).