title: TusA (YhhP) and IscS are required for molybdenum cofactor-dependent base-analog detoxification.
abstract: Lack of molybdenum cofactor (Moco) in Escherichia coli leads to hypersensitivity to the mutagenic and toxic effects of N-hydroxylated base analogs, such as 6-N-hydroxylaminopurine (HAP). This phenotype is due to the loss of two Moco-dependent activities, YcbX and YiiM, that are capable of reducing HAP to adenine. Here, we describe two novel HAP-sensitive mutants containing a defect in iscS or tusA (yhhP) gene. IscS is a major L-cysteine desulfurase involved in iron-sulfur cluster synthesis, thiamine synthesis, and tRNA thiomodification. TusA is a small sulfur-carrier protein that interacts with IscS. We show that both IscS and TusA operate within the Moco-dependent pathway. Like other Moco-deficient strains, tusA and iscS mutants are HAP sensitive and resistant to chlorate under anaerobic conditions. The base-analog sensitivity of iscS or tusA strains could be suppressed by supplying exogenous L-cysteine or sulfide or by an increase in endogenous sulfur donors (cysB constitutive mutant). The data suggest that iscS and tusA mutants have a defect in the mobilization of sulfur required for active YcbX/YiiM proteins as well as nitrate reductase, presumably due to lack of functional Moco. Overall, our data imply a novel and indispensable role of the IscS/TusA complex in the activity of several molybdoenzymes.
authors.affiliation: Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, 27709.
authors.forename: Stanislav G
authors.initials: SG
authors.lastname: Kozmin
authors.forename: Elena I
authors.initials: EI
authors.lastname: Stepchenkova
authors.forename: Roel M
authors.initials: RM
authors.lastname: Schaaper
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000693:Anaerobiosis; D013437:Carbon-Sulfur Lyases / Q000235:genetics* / Q000378:metabolism; D002704:Chlorates / Q000494:pharmacology; D003067:Coenzymes / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008667:Metalloproteins / Q000378:metabolism*; D000090006:Molybdenum Cofactors; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D011621:Pteridines / Q000378:metabolism*; D015398:Signal Transduction; D013455:Sulfur / Q000378:metabolism
chemical_list: D000225:Adenine; D013437:Carbon-Sulfur Lyases; D002704:Chlorates; D003067:Coenzymes; D003545:Cysteine; D029968:Escherichia coli Proteins; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D009153:Mutagens; D011621:Pteridines; D013455:Sulfur; C551794:TusA protein, E coli; C032610:6-N-hydroxylaminopurine; C022261:molybdopterin; C080546:cysteine desulfurase; C022842:chloric acid
keywords: 6-N-hydroxylaminopurine (HAP) sensitivity; IscS cysteine desulfurase; TusA sulfur-carrier protein.; chlorate resistance; molybdenum cofactor (Moco) biosynthesis
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