The role of Nif proteins in nitrogenase maturation

L.M. RUBIO; J.A. HERNANDEZ; B. SOBOH; D. ZHAO; R.Y. IGARASHI; L. CURATTI; P.W. LUDDEN

Biological nitrogen fixation: towards poverty alleviation through sustainable agriculture

Springer

Año: 2008;

The major part of biological nitrogen fixation is catalyzed by the molybdenum nitrogenase, which is composed of two oxygen-labile metalloproteins: the MoFe protein and the Fe protein. The MoFe protein carries at its active site the most complex metallocluster known in biology: the iron-molybdenum cofactor (FeMo-co). The Fe protein is a dimer of the nifH gene product that contains a single [4Fe-4S] center coordinated between the two subunits. The structural genes for the MoFe protein, nifD and nifK, do not seem to be required for the biosynthesis of FeMo-co. It is accepted that FeMo-co is assembled elsewhere in the cells and then incorporated into a FeMo-co deficient apo-MoFe protein. A number of nitrogen fixation (nif) genes are required for the biosynthesis of FeMo-co and the maturation of the nitrogenase component proteins. Roles for the nifB, nifQ, nifX, nifN, nifE, nifV, and nifH genes in FeMo-co biosynthesis will be discussed. The nifY/nafY, and nifH genes are involved in MoFe protein maturation while nifM seems to be required for the maturation of the Fe protein. The products of the nifU and nifS genes are proposed to have a general role in the biosynthesis of [Fe-S] clusters for the nitrogenase components.