Structural analysis of a protein in which the usual rare earth cofactor is replaced with europium
Determination of structure and kinetics reveals the effects of several different rare earths on catalytic activity.
Most organisms depend on commonly occurring substances, but some bacteria use rare earth elements (REEs) such as lanthanum, cerium or europium as cofactors of metalloenzymes - enzymes that catalyze chemical reactions with the help of a metal ion. One of these is a methanol dehydrogenase (MDH), an enzyme used by the bacteria in harvesting energy. Scientists at the Max Planck Institute for Medical Research in Heidelberg and their collaborators* have now determined the structure and kinetics of an MDH with a europium ion as cofactor in the active site, the first ever example of an enzyme using this element. By comparison with previous analyses, they were able to establish that while the enzyme is 200 times slower than with other rare earth elements the overall structure remains the same. This lower activity must therefore be the result of very subtle changes active site chemistry. The observed variations in the protein’s efficiency in catalyzing the chemical reaction for which it is required, probably reflect the adaptation of the bacteria to the lighter REEs, which are more abundant in the environment.
* from the Ludwig-Maximilians-Universität in Munich and the Institute for Water and Wetland Research in Nijmegen