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Characterization of a Mo‐Nitrogenase Variant Containing a Citrate‐Substituted Cofactor
Author(s) -
Liedtke Jasper,
Lee Chi Chung,
Tanifuji Kazuki,
Jasniewski Andrew J.,
Ribbe Markus W.,
Hu Yilin
Publication year - 2021
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.202000598
Subject(s) - nitrogenase , azotobacter vinelandii , cofactor , chemistry , stereochemistry , ligand (biochemistry) , crystallography , biochemistry , enzyme , nitrogen fixation , organic chemistry , nitrogen , receptor
Nitrogenase converts N 2 to NH 3 , and CO to hydrocarbons, at its cofactor site. Herein, 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.