Electron transfer and half-reactivity in nitrogenase

Clarke, Tom ORCID: https://orcid.org/0000-0002-6234-1914, Fairhurst, Shirley, Lowe, David J., Watmough, Nick and Eady, Robert R. (2011) Electron transfer and half-reactivity in nitrogenase. Biochemical Society Transactions, 39 (1). pp. 201-206. ISSN 0300-5127

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Nitrogenase is a globally important enzyme that catalyses the reduction of atmospheric dinitrogen into ammonia and is thus an important part of the nitrogen cycle. The nitrogenase enzyme is composed of a catalytic molybdenum–iron protein (MoFe protein) and a protein containing an [Fe4–S4] cluster (Fe protein) that functions as a dedicated ATP-dependent reductase. The current understanding of electron transfer between these two proteins is based on stopped-flow spectrophotometry, which has allowed the rates of complex formation and electron transfer to be accurately determined. Surprisingly, a total of four Fe protein molecules are required to saturate one MoFe protein molecule, despite there being only two well-characterized Fe-protein-binding sites. This has led to the conclusion that the purified Fe protein is only half-active with respect to electron transfer to the MoFe protein. Studies on the electron transfer between both proteins using rapid-quench EPR confirmed that, during pre-steady-state electron transfer, the Fe protein only becomes half-oxidized. However, stopped-flow spectrophotometry on MoFe protein that had only one active site occupied was saturated by approximately three Fe protein equivalents. These results imply that the Fe protein has a second interaction during the initial stages of mixing that is not involved in electron transfer.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
UEA Research Groups: Faculty of Science > Research Groups > Molecular Microbiology
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Faculty of Science > Research Groups > Energy Materials Laboratory
Depositing User: Users 2731 not found.
Date Deposited: 14 Feb 2011 14:03
Last Modified: 21 Apr 2023 06:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/21344
DOI: 10.1042/BST0390201

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