HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chan, J. M. Articles by Seefeldt, L. C. Search for Related Content PubMed PubMed Citation Articles by Chan, J. M. Articles by Seefeldt, L. C. Social Bookmarking                      What's this?

J Biol Chem, Vol. 274, Issue 25, 17593-17598, June 18, 1999

Evidence That MgATP Accelerates Primary Electron Transfer in a Clostridium pasteurianum Fe Protein-Azotobacter vinelandii MoFe Protein Nitrogenase Tight Complex

From the Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322

The nitrogenase catalytic cycle involves binding of the iron (Fe) protein to the molybdenum-iron (MoFe) protein, transfer of a single electron from the Fe protein to the MoFe protein concomitant with the hydrolysis of at least two MgATP molecules, followed by dissociation of the two proteins. Earlier studies found that combining the Fe protein isolated from the bacterium Clostridium pasteurianum with the MoFe protein isolated from the bacterium Azotobacter vinelandii resulted in an inactive, nondissociating Fe protein-MoFe protein complex. In the present work, it is demonstrated that primary electron transfer occurs within this nitrogenase tight complex in the absence of MgATP (apparent first-order rate constant k = 0.007 s¹) and that MgATP accelerates this electron transfer reaction by more than 10,000-fold to rates comparable to those observed within homologous nitrogenase complexes (k = 100 s¹). Electron transfer reactions were confirmed by EPR spectroscopy. Finally, the midpoint potentials (E_m) for the Fe protein [4Fe-4S]^2+/+ cluster and the MoFe protein P^2+/N cluster were determined for both the uncomplexed and complexed proteins and with or without MgADP. Calculations from electron transfer theory indicate that the measured changes in E_m are not likely to be sufficient to account for the observed nucleotide-dependent rate accelerations for electron transfer.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				T. J. Lowery, P. E. Wilson, B. Zhang, J. Bunker, R. G. Harrison, A. C. Nyborg, D. Thiriot, and G. D. Watt Nitrogen Fixation Special Feature: Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state PNAS, November 14, 2006; 103(46): 17131 - 17136. [Abstract] [Full Text] [PDF]

				J. G. Grossmann, S. S. Hasnain, F. K. Yousafzai, and R. R. Eady Evidence for the Selective Population of FeMo Cofactor Sites in MoFe Protein and Its Molecular Recognition by the Fe Protein in Transition State Complex Analogues of Nitrogenase J. Biol. Chem., February 23, 2001; 276(9): 6582 - 6590. [Abstract] [Full Text] [PDF]