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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.


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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).

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