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Description (originally from EcoCyc[1]) MoaB

Comments (originally from EcoCyc[1]) Molybdenum and tungsten cofactors of all enzymes that require one or the other for activity are present in an oxidized state as molybdate or tungstate ions that are chelated by the cis-dithiolene moiety of a molybdenum cofactor. The particular cofactor that occurs in Escherichia coli is molybdopterin guanine dinucleotide. This and other molybdenum cofactors are so extremely unstable that they have not been isolated in pure form, and only the outline of their pathway of biosynthesis has been elucidated: a modified guanine in several steps is converted to a sulfur-free pterin called precursor Z; then by a subsequent series of reactions two sulfhydryl groups are added yielding molybdopterin with it cis-dithiolene moiety and then a guanyl group is added yielding molybdopeterin guanine dinucleotide, the active molybdenum cofactor of E. coli.

Enzymes encoded by the moaABCD, mobAB, mogA, and moeAB operons all participate in the synthesis of molybdopterin guanine dinucleotide. A mutational block in any of these proteins leads to a loss of function of all molybdenum enzymes.

Together MoaA, MoaB, and MoaC convert a guanine derivative to precursor Z [2][3][4] resolution.


  1. 1.0 1.1 EcoCyc (release 11.1; 2007) Keseler, IM et al. (2005) Nucleic Acids Res. 33(Database issue):D334-7
  2. Rieder, C et al. (1998) Rearrangement reactions in the biosynthesis of molybdopterin--an NMR study with multiply 13C/15N labelled precursors. Eur. J. Biochem. 255 24-36 PubMed
  3. Bader, G et al. (2004) Structure of the molybdenum-cofactor biosynthesis protein MoaB of Escherichia coli. Acta Crystallogr. D Biol. Crystallogr. 60 1068-75 PubMed
  4. Sanishvili, R et al. (2004) The crystal structure of Escherichia coli MoaB suggests a probable role in molybdenum cofactor synthesis. J. Biol. Chem. 279 42139-46 PubMed

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