Peptidyl-prolyl cis/trans isomerases (PPIases) play a pivotal role in catalyzing the correct folding of many prokaryotic and eukaryotic proteins that are implicated in a variety of biological functions, ranging from cell cycle regulation to bacterial infection. The nif accessory protein NifM, which is essential for the biogenesis of a functional NifH component of nitrogenase, is a PPIase. To un...

NifH (dinitrogenase reductase) has three important roles in the nitrogenase enzyme system. In addition to its role as the obligate electron donor to dinitrogenase, NifH is required for the iron-molybdenum cofactor (FeMo-co) synthesis and apodinitrogenase maturation. We have investigated the requirement of the Fe-S cluster of NifH for these processes by preparing apoNifH. The 4Fe-4S cluster of N...

Biological nitrogen fixation is an important source of fixed nitrogen for the biosphere. Microorganisms catalyse biological nitrogen fixation with the enzyme nitrogenase, which has been highly conserved through evolution. Cloning and sequencing of one of the nitrogenase structural genes, nifH, has provided a large, rapidly expanding database of sequences from diverse terrestrial and aquatic env...

Flooding impacts soil microbial communities, but its effect on endophytic communities has rarely been explored. This work addresses the effect of flooding on the abundance and diversity of endophytic diazotrophic communities on rice plants established in a greenhouse experiment. The nifH gene was significantly more abundant in roots after flooding, whereas the nifH gene copy numbers in leaves w...

The distribution of nitrogen-fixing microorganisms in the Chesapeake Bay was investigated using fingerprints from a nifH microarray comprised of 706 60-mer oligonucleotide nifH probes representing cultivated organisms and environmental clones from different nifH clusters. Diverse nifH targets, amplified from samples using degenerate nifH primers, were detected in water column and sediment sampl...

L. Sibold, M. Henriquet, O. Possot, and J.-P. Aubert (Res. Microbiol. 142:5-12, 1991) cloned and sequenced two nifH-homologous open reading frames (ORFs) from Methanosarcina barkeri 227. Phylogenetic analysis of the deduced amino acid sequences of the nifH ORFs from M. barkeri showed that nifH1 clusters with nifH genes from alternative nitrogenases, while nifH2 clusters with nifH1 from the gram...

The His-tag MoFe protein expressed by the nifH deletion strain Azotobacter vinelandii DJ1165 (Delta(nifH) MoFe protein) was purified in large quantity. The alpha(2)beta(2) tetrameric Delta(nifH) MoFe protein is FeMoco-deficient based on metal analysis and the absence of the S = 3/2 EPR signal, which arises from the FeMo cofactor center in wild-type MoFe protein. The Delta(nifH) MoFe protein con...