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.
Skip Nav Destination
Article navigation
February 2011
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
Conference Article|
January 19 2011
Electron transfer and half-reactivity in nitrogenase
Thomas A. Clarke;
Thomas A. Clarke
1
*Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
1To whom correspondence should be addressed (email tom.clarke@uea.ac.uk).
Search for other works by this author on:
Shirley Fairhurst;
Shirley Fairhurst
†Department of Biological Chemistry, John Innes Centre, Colney, Norwich NR4 7UH, U.K.
Search for other works by this author on:
David J. Lowe;
David J. Lowe
†Department of Biological Chemistry, John Innes Centre, Colney, Norwich NR4 7UH, U.K.
Search for other works by this author on:
Nicholas J. Watmough;
Nicholas J. Watmough
*Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
Search for other works by this author on:
Robert R. Eady
Robert R. Eady
‡School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, U.K.
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
October 25 2010
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2011 Biochemical Society
2011
Biochem Soc Trans (2011) 39 (1): 201–206.
Article history
Received:
October 25 2010
Citation
Thomas A. Clarke, Shirley Fairhurst, David J. Lowe, Nicholas J. Watmough, Robert R. Eady; Electron transfer and half-reactivity in nitrogenase. Biochem Soc Trans 1 February 2011; 39 (1): 201–206. doi: https://doi.org/10.1042/BST0390201
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.