Comparison of the sequences of the Aspergillus nidulans hxB and Drosophila melanogaster ma-l genes with nifS from Azotobacter vinelandii suggests a mechanism for the insertion of the terminal sulphur atom in the molybdopterin cofactor.
The molybdopterin cofactor (MoCF) is required for the activity of a variety of oxidoreductases. The xanthine oxidase class of molybdoenzymes requires the MoCF to have a terminal, cyanolysable sulphur ligand. In the sulphite oxidase/nitrate reductase class, an oxygen is present in the same position. Mutations in both the ma-l gene of Drosophila melanogaster and the hxB gene of Aspergillus nidulans result in loss of activities of all molybdoenzymes that necessitate a cyanolysable sulphur in the active centre. The ma-l and hxB genes encode highly similar proteins containing domains common to pyridoxal phosphate-dependent cysteine transulphurases, including the cofactor binding site and a conserved cysteine, which is the putative sulphur donor. Key similarities were found with NifS, the enzyme involved in the generation of the iron-sulphur centres in nitrogenase. These similarities suggest an analogous mechanism for the generation of the terminal molybdenum-bound sulphur ligand. We have identified putative homologues of these genes in a variety of organisms, including humans. The human homologue is located in chromosome 18.q12.
Amrani
L
L
Institut de Génétique et Microbiologie, Université Paris-Sud XI, UMR-CNRS 8621, Centre Universitaire d'Orsay, Bâtiment 409, 91405 Orsay Cedex, France.
Primus
J
J
Glatigny
A
A
Arcangeli
L
L
Scazzocchio
C
C
Finnerty
V
V
D000595:Amino Acid Sequence; D000818:Animals; D001233:Aspergillus nidulans / Q000235:genetics*; D016948:Azotobacter vinelandii / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D003067:Coenzymes; D004331:Drosophila melanogaster / Q000235:genetics*; D005798:Genes, Bacterial; D005800:Genes, Fungal; D008667:Metalloproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D000090006:Molybdenum Cofactors; D011621:Pteridines / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013455:Sulfur / Q000737:chemistry
D001426:Bacterial Proteins; D003067:Coenzymes; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D011621:Pteridines; D013455:Sulfur; C080001:nifS protein, Bacteria; C022261:molybdopterin