Similar but Not the Same: First Kinetic and Structural Analyses of a Methanol Dehydrogenase Containing a Europium Ion in the Active Site

• Published in: Chembiochem : a European journal of chemical biology Vol. 19; no. 11; pp. 1147 - 1153
• Main Authors: Jahn, Bérénice, Pol, Arjan, Lumpe, Henning, Barends, Thomas R. M., Dietl, Andreas, Hogendoorn, Carmen, Op den Camp, Huub J. M., Daumann, Lena J.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 04.06.2018; John Wiley and Sons Inc
• Subjects: Bacteria; Calcium; Catalysis; Cerium; Circular dichroism; Coordination numbers; Crystal structure; Cultivation; Dehydrogenase; Dehydrogenases; Dichroism; Europium; Inductively coupled plasma mass spectrometry; lanthanides; Mass spectrometry; Mass spectroscopy; Methanol; Methanol dehydrogenase; methanol dehydrogenases; oxidoreductases; Purification; Rare earth elements; rare earths; oxidoreductases; methanol dehydrogenases; europium; lanthanides; rare earths
• ISSN: 1439-4227; 1439-7633
• DOI: 10.1002/cbic.201800130

Since the discovery of the biological relevance of rare earth elements (REEs) for numerous different bacteria, questions concerning the advantages of REEs in the active sites of methanol dehydrogenases (MDHs) over calcium(II) and of why bacteria prefer light REEs have been a subject of debate. Here we report the cultivation and purification of the strictly REE‐dependent methanotrophic bacterium Methylacidiphilum fumariolicum SolV with europium(III), as well as structural and kinetic analyses of the first methanol dehydrogenase incorporating Eu in the active site. Crystal structure determination of the Eu‐MDH demonstrated that overall no major structural changes were induced by conversion to this REE. Circular dichroism (CD) measurements were used to determine optimal conditions for kinetic assays, whereas inductively coupled plasma mass spectrometry (ICP‐MS) showed 70 % incorporation of Eu in the enzyme. Our studies explain why bacterial growth of SolV in the presence of Eu3+ is significantly slower than in the presence of La3+/Ce3+/Pr3+: Eu‐MDH possesses a decreased catalytic efficiency. Although REEs have similar properties, the differences in ionic radii and coordination numbers across the series significantly impact MDH efficiency. Methanotrophs and lanthanides: Although rare earth elements (REEs) have similar properties, the differences in ionic radii and coordination numbers across the series have a significant impact on the activities of methanol dehydrogenase enzymes. This in turn can affect the growth rates of REE‐dependent bacteria.