Title
Similar but not the same: First Kinetic and Structural Analyses of a Methanol Dehydrogenase Containing a Europium Ion in the Active Site
Author
Bérénice Jahn, Arjan Pol, Henning Lumpe, Thomas Barends, Andreas Dietl, Carmen Hogendoorn, Huub Op den Camp, Lena Daumann
Year
2018
Journal
ChemBioChem
Abstract
Since the discovery of the biological relevance of rare earth elements (REE) for numerous different bacteria, the questions of the advantage of REE in the active site of methanol dehydrogenase (MDH) over calcium(II) and why bacteria prefer light REE have been a subject of debate. Here we report the cultivation and purification of the strictly REE-dependent methanotrophic bacterium Methyl-acidiphilum fumariolicum SolV with europium(III) as well as structural and kinetic analyses of the first Eu-substituted methanol dehydrogenase. Crystal structure determination of the Eu-MDH demonstrated that overall no major structural changes were induced by converting to this REE. Circular Dichroism (CD) measurements were used to determine optimal conditions for kinetic assays and inductively-coupled plasma mass-spectrometry (ICP-MS) showed 70% incorporation of Eu in the enzyme. Our studies explain why bacterial growth of SolV with Eu3+ is significantly slower than with La3+/Ce3+/Pr3+: Eu-MDH possesses a decreased catalytic efficiency and affinity for the substrate. Although rare earth elements have similar properties, the differences in ionic radii and coordination numbers across the series significantly impact MDH efficiency.
Instrument
J-810
Keywords
Circular dichroism, Chemical stability, Biochemistry