Evidence for a dynamic role for homocitrate during nitrogen fixation: The effect of substitution at the α-Lys426 position in MoFe-protein of Azotobacter vinelandii

Marcus Durrant, Amanda Francis, David Lowe, William Newton, Karl Fisher

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

Although it is generally accepted that the active site of nitrogenase is located on the FeMo-cofactor, the exact site(s) of N2 binding and reduction remain the subject of continuing debate, with both molybdenum and iron atoms being suggested as key players. The current consensus favours binding of acetylene and some other non-biologically relevant substrates to the central iron atoms of the FeMo-cofactor [Dos Santos, Igarashi, Lee, Hoffman, Seefeldt and Dean (2005) Ace. Chem. Res. 38, 208-214]. The reduction of N2 is, however, a more demanding process than reduction of these alternative substrates because it has a much higher activation energy and does not bind until three electrons have been accumulated on the enzyme. The possible conversion of bidentate into monodentate homocitrate on this three electron-reduced species has been proposed to free up a binding site for N 2 on the molybdenum atom. One of the features of this hypothesis is that α-Lys426 facilitates chelate ring opening and subsequent orientation of the monodentate homocitrate by forming a specific hydrogen bond to the homocitrate -CH2CH2CO2- carboxylate group. In support of this concept, we show that mutation of α-Lys426 can selectively perturb N2 reduction without affecting acetylene reduction. We interpret our experimental observations in the light of a detailed molecular mechanics modelling study of the wild-type and altered MoFe-nitrogenases.
Original languageEnglish
Pages (from-to)261-270
JournalBiochemical Journal
Volume397
Issue number2
DOIs
Publication statusPublished - Jul 2006

Fingerprint

Dive into the research topics of 'Evidence for a dynamic role for homocitrate during nitrogen fixation: The effect of substitution at the α-Lys426 position in MoFe-protein of Azotobacter vinelandii'. Together they form a unique fingerprint.

Cite this