Evidence for MoeA-dependent formation of the molybdenum cofactor from molybdate and molybdopterin in Escherichia coli

The function of the MoeA protein in the biosynthesis of the molybdenum cofactor (MoCo) was analyzed in vitro, using purified His(6)-MoeA from Escherichia coli, molybdopterin (MPT) isolated from buttermilk xanthine oxidase and molybdate. The formation of MoCo was monitored by the reconstitution of nitrate reductase activity in extracts of the Neurospora crassa nit-1 mutant. Formation of MoCo from MPT and molybdate required MoeA and L-cysteine or glutathione. The reaction proceeded at micromolar molybdate levels and was time- and MoeA concentration-dependent. A physical interaction between MoeA and MPT was demonstrated by HPLC analysis of MoeA-bound MPT.