NifB gene product

Figure 12 illustrates the current model of FeMo cofactor biosynthesis, a process independent of the production of MoFe protein polypeptides, which starts with the mobihzation of iron and sulfur and the assembly of Fe/S fragments by NifS and NifU. These Fe/S fragments are transferred to NifB nifB gene product), which is subsequently involved in the production of the Fe/S core of the FeMo cofactor (designated NifB cofactor) that probably contains all of... 

The detailed characterization of the FeMoco site has involved parallel studies of the site within the protein and in its extracted form. The authentication of the extracted FeMoco involves the production and use of mutant organisms that make an inactive FeMo protein that contains all subunits and P clusters, but lacks the FeMoco sites.A mutant of Azotobacter vinelandii called UW-45 (UW = C/niversity of Wisconsin) was first used to assay for isolated FeMoco.Since several genes are involved in specifying FeMoco biosynthesis, mutants lacking these genes produce FeMo protein either lacking FeMoco or having a defective version of FeMoco. Mutants such as NifB of Klebsiella pneumoniae lack cofactor, and an inactive apo protein can be isolated from them. 

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