Taxonomic distribution of proteins containing Nfu_N domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing Nfu_N domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Iron-sulfur cluster assembly: NifU-directed activation of the nitrogenaseFe protein.

Dos Santos PC, Smith AD, Frazzon J, Cash VL, Johnson MK, Dean DR
J Biol Chem. 2004; 279: 19705-11

The NifU protein is a homodimer that is proposed to provide a molecularscaffold for the assembly of [Fe-S] clusters uniquely destined for thematuration of the nitrogenase catalytic components. There are threedomains contained within NifU, with the N-terminal domain exhibiting ahigh degree of primary sequence similarity to a related family of [Fe-S]cluster biosynthetic scaffolds designated IscU. The C-terminal domain ofNifU exhibits sequence similarity to a second family of proposed [Fe-S]cluster biosynthetic scaffolds designated Nfu. Genetic experimentsdescribed here involving amino acid substitutions within the N-terminaland C-terminal domains of NifU indicate that both domains can separatelyparticipate in nitrogenase-specific [Fe-S] cluster formation, although theN-terminal domain appears to have the dominant function. These in vivoexperiments were supported by in vitro [Fe-S] cluster assembly andtransfer experiments involving the activation of an apo-form of thenitrogenase Fe protein.

Subcellular compartmentalization of human Nfu, an iron-sulfur clusterscaffold protein, and its ability to assemble a [4Fe-4S] cluster.

Tong WH, Jameson GN, Huynh BH, Rouault TA
Proc Natl Acad Sci U S A. 2003; 100: 9762-7

Iron-sulfur (Fe-S) clusters serve as cofactors in many proteins that haveimportant redox, catalytic, and regulatory functions. In bacteria,biogenesis of Fe-S clusters is mediated by multiple gene products encodedby the isc and nif operons. In particular, genetic and biochemical studiessuggest that IscU, Nfu, and IscA function as scaffold proteins forassembly and delivery of rudimentary Fe-S clusters to target proteins.Here we report the characterization of human Nfu. A combination ofbiochemical and spectroscopic techniques, including UV-visible absorptionand 57Fe Mossbauer spectroscopies, have been used to investigate theability of purified human Nfu to assemble Fe-S clusters. The resultssuggest that Nfu can assemble approximately one labile [4Fe-4S] clusterper two Nfu monomers, and support the proposal that Nfu is an alternativescaffold protein for assembly of clusters that are subsequently used formaturation of targeted Fe-S proteins. Analyses of genomic DNA,transcripts, and translation products indicate that alternative splicingof a common pre-mRNA results in synthesis of two Nfu isoforms withdistinct subcellular localizations. Isoform I is localized in themitochondria, whereas isoform II is present in the cytosol and thenucleus. These results, together with previous reports of subcellulardistributions of isoforms of human IscS and IscU in mitochondria, cytosol,and nucleus suggest that the Fe-S cluster assembly machineries arecompartmentalized in higher eukaryotes.