NifB-dependent synthesis of the iron-molybdenum cofactor of nitrogenase

CURATTI LEONARDO; LUDDEN PAUL; RUBIO LUIS

Biological nitrogen fixation: towards poverty alleviation through sustainable agriculture

Springer

Año: 2008; p. 329 - 330

The major part of biological nitrogen fixation is catalyzed by the molybdenum nitrogenase, which carries at its active site the most complex metallocluster known in biology: the iron-molybdenum cofactor (FeMo-co), composed of 7 Fe, 9 S, 1 Mo, 1 homocitrate, and 1 light atom (C, N, or O). At least seven nitrogen fixation (nif) genes, nifB, nifE, nifN, nifH, nifQ, nifV, and nifX are involved in FeMo-co biosynthesis and the formation of an active dinitrogenase component. Among these, the nifB gene has been long recognized as crucial for nitrogen fixation because nifB participates in an early synthetic step that is common to the biosyntheses of FeMo-co and the analogous iron-vanadium (FeV-co) and iron-only (FeFe-co) cofactors, carried by the vanadium and the iron-only nitrogenases, respectively. Recently, we have achieved the purification of NifB and the development of a NifB activity assay that drives the synthesis of FeMo-co in vitro and the formation of active nitrogenase. An important observation from this assay is that FeMo-co assembly involves radical chemistry. The synthesis in vitro of FeMo-co from its simple constituents, Fe, S, Mo, and homocitrate, reported here, entails definitive progress in the study of nitrogen fixation and the assembly of complex metalloclusters in general.