Characterisation of the mob locus of Rhodobacter sphaeroides WS8: mobA is the only gene required for molybdopterin guanine dinucleotide synthesis.
The mob genes of several bacteria have been implicated in the conversion of molybdopterin to molybdopterin guanine dinucleotide. The mob locus of Rhodobacter sphaeroides WS8 comprises three genes, mobABC. Chromosomal in-frame deletions in each of the mob genes have been constructed. The mobA mutant strain has inactive DMSO reductase and periplasmic nitrate reductase activities (both molybdopterin guanine dinucleotide-requiring enzymes), but the activity of xanthine dehydrogenase, a molybdopterin enzyme, is unaffected. The inability of a mobA mutant to synthesise molybdopterin guanine dinucleotide is confirmed by analysis of cell extracts of the mobA strain for molybdenum cofactor forms following iodine oxidation. Mutations in mobB and mobC are not impaired for molybdoenzyme activities and accumulate wild-type levels of molybdopterin and molybdopterin guanine dinucleotide, indicating they are not compromised in molybdenum cofactor synthesis. In the mobA mutant strain, the inactive DMSO reductase is found in the periplasm, suggesting that molybdenum cofactor insertion is not necessarily a pre-requisite for export.
Buchanan
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G
Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
Kuper
J
J
Mendel
R R
RR
Schwarz
G
G
Palmer
T
T
D003001:Cloning, Molecular; D003067:Coenzymes; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D006150:Guanine Nucleotides / Q000096:biosynthesis* / Q000378:metabolism; D007455:Iodine / Q000378:metabolism; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins / Q000032:analysis / Q000378:metabolism; D000090006:Molybdenum Cofactors; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D019897:Periplasm / Q000201:enzymology; D011621:Pteridines / Q000032:analysis / Q000378:metabolism; D011622:Pterins / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D014968:Xanthine Dehydrogenase / Q000378:metabolism
D003067:Coenzymes; D006150:Guanine Nucleotides; D007455:Iodine; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D050901:Nitrate Reductase; D009565:Nitrate Reductases; D010088:Oxidoreductases; D011621:Pteridines; D011622:Pterins; D014968:Xanthine Dehydrogenase; C063761:molybdopterin guanine dinucleotide; C022261:molybdopterin; C045664:dimethyl sulfoxide reductase