The NifX Protein is Involved in the Final Stages of FeMo-cofactor Transport to the MoFe Protein

Abstract

Abstract:The nitrogenase enzyme catalyzes the reduction of dinitrogen to ammonia and is composed of the Fe and MoFe proteins. The iron molybdenum cofactor (FeMo-co) of the MoFe protein is the site of active substrate reduction. The NifX protein has also been suggested to have a role in the FeMo-co synthesis, although its exact role is still open to investigation. We attempted to understand the role of NifX by determining the specific interactions it may have with other Nif proteins involved in FeMo-co synthesis, such as NifD, NifK, NifN, NifDK and NifH. Using the BacterioMatch Two-Hybrid System, a translationally fused construct of NifX with the N-terminal α-RNAP of the pTRG target vector was made and its interaction was tested with the NifDK fusion protein, translationally fused to the λCI of the pBT vector. The strength of the interaction, as determined by measuring the β-galactosidase activity, demonstrated that direct protein-protein interaction exists between NifDK and NifX proteins; the extent of interaction between NifK and NifX proteins was much higher than between NifD and NifX, when individually tested; also, reduced interaction was found between NifH and NifX.

Proteomic and Mutant Analysis of Hydrogenase Maturation Protein Gene hypE in Symbiotic Nitrogen Fixation of Mesorhizobium huakuii

“…Two genes, MCHK_2003 and MCHK_5582 , encoding for nitrogen utilization are up-regulated, while all the proteins relative to electron transport and nitrogen fixation ammonia assimilation are down-regulated in the mutant bacteroids. The nitrogenase enzyme is composed of the Fe and MoFe proteins [ 25 ]. Three key nitrogen-fixation genes, nifX , nifD , and nifK , are required for nitrogenase component proteins, and nifE is required for the synthesis of the iron–molybdenum cofactor (FeMoco) of nitrogenase.…”

Bd oxidase homologue of photosynthetic purple sulfur bacterium Allochromatium vinosum is co-transcribed with a nitrogen fixation related gene

“…It has been reported that the small molecule binding domain of nifX has a phyletic widespread distribution which indicates an ancient origin or extensive dissemination by horizontal gene transfer during evolution (Lahiri et al 2007). Molecular evolutionary analysis of the chlorophyll biosynthetic pathway strongly supports that the photosystem of the anoxygenic purple bacteria is the most ancient (Xiong et al 2000).…”