<p>A number of proteins involved in the biosynthesis of metallo cofactors havebeen shown [<cite idref="PUB00000168"/>, <cite idref="PUB00002946"/>] to be evolutionary related. These include:<ul><li>Bacterial and archebacterial protein moaA, which is involved in the biosynthesis of the molybdenum cofactor (molybdopterin; MPT).</li><li> <taxon tax_id="3702">Arabidopsis thaliana</taxon> (Mouse-ear cress) cnx2, a protein involved in molybdopterin biosynthesis and which is highly similar to moaA.</li><li> <taxon tax_id="1423">Bacillus subtilis</taxon> narA, which seems to be the moaA ortholog in that bacteria.</li><li>Bacterial protein nifB (or fixZ) which is involved in the biosynthesis of the nitrogenase iron-molybdenum cofactor.</li><li>Bacterial protein pqqE which is involved in the biosynthesis of the cofactor pyrrolo-quinoline-quinone (PQQ).</li><li> <taxon tax_id="2261">Pyrococcus furiosus</taxon> cmo, a protein involved in the synthesis of a molybdopterin-based tungsten cofactor.</li><li> <taxon tax_id="6239">Caenorhabditis elegans</taxon> hypothetical protein F49E2.1.</li></ul>These proteins share, in their N-terminal region, a conserved domain thatcontains three cysteines. In moaA, these cysteines have been shown to be important for biological activity by binding a [4Fe-4S] cluster [<cite idref="PUB00015124"/>]. The three cysteines each coordinate one Fe, while S-adenosylmethionine is the fourth ligand to the cluster and binds to its unique Fe as an N/O chelate.</p> MoaA/nifB/pqqE, iron-sulphur binding, conserved site