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DOE OSTI · 1785240

Characterization of a Mo-Nitrogenase Variant Containing a Citrate-Substituted Cofactor

Liedtke, Jasper·Lee, Chi Chung·Tanifuji, Kazuki·Jasniewski, Andrew J.·Ribbe, Markus W.·Hu, Yilin
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Abstract

Nitrogenase converts N 2 to NH 3 , and CO to hydrocarbons, at its cofactor site. In this work, we report a biochemical and spectroscopic characterization of a Mo-nitrogenase variant expressed in an Azotobacter vinelandii strain containing a deletion of nifV, the gene encoding the homocitrate synthase. Designated NifDK Cit , the catalytic component of this Mo-nitrogenase variant contains a citrate-substituted cofactor analogue. Activity analysis of NifDK Cit reveals a shift of CO reduction from H 2 evolution toward hydrocarbon formation and an opposite shift of N 2 reduction from NH 3 formation toward H 2 evolution. Consistent with a shift in the Mo K-edge energy of NifDK Cit relative to that of its wild-type counterpart, EPR analysis demonstrates a broadening of the line-shape and a decrease in the intensity of the cofactor-originated S=3/2 signal, suggesting a change in the spin properties of the cofactor upon citrate substitution. These observations point to a crucial role of homocitrate in substrate reduction by nitrogenase and the possibility to tune product profiles of nitrogenase reactions via organic ligand substitution.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYammoniacarbon monoxidecofactorshydrocarbonsmolybdenum nitrogenase

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Liedtke, Jasper, Lee, Chi Chung, Tanifuji, Kazuki, Jasniewski, Andrew J., Ribbe, Markus W., Hu, Yilin. 2020-09-12. Characterization of a Mo-Nitrogenase Variant Containing a Citrate-Substituted Cofactor. https://doi.org/10.1002/cbic.202000598

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