期刊
MICROBIOLOGYOPEN
卷 2, 期 5, 页码 743-755出版社
WILEY
DOI: 10.1002/mbo3.108
关键词
6-N-hydroxylaminopurine (HAP) sensitivity; chlorate resistance; IscS cysteine desulfurase; molybdenum cofactor (Moco) biosynthesis; TusA sulfur-carrier protein
类别
资金
- Intramural Research Program of the National Institute of Environmental Health Sciences (NIEHS) [ES050170]
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.
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