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Mycobacterium tuberculosis FurA Autoregulates Its Own Expression. Claudia Sala, 2003.The furA-katG region of Mycobacterium tuberculosis, encoding a Fur-like protein and the catalase-peroxidase, is highly conserved among mycobacteria . Both genes are induced upon oxidative stress . In this work we analyzed the M . tuberculosis furA promoter region . DNA fragments were cloned upstream of the luciferase reporter gene, and promoter activity in Mycobacterium smegmatis was measured in both the presence and absence of oxidative stress . The shortest fragment containing an inducible promoter extends 45 bp upstream of furA . In this region, -35 and -10 promoter consensus sequences can be identified, as well as a 23-bp AT-rich sequence that is conserved in the nonpathogenic but closely related M . smegmatis . M . tuberculosis FurA was purified and found to bind upstream of furA by gel shift analysis . A ca . 30-bp DNA sequence, centered on the AT-rich region, was essential for FurA binding and protected by FurA in footprinting analysis . Peroxide treatment of FurA abolished DNA binding . Three different AT-rich sequences mutagenized by site-directed mutagenesis were constructed . In each mutant, both M . tuberculosis FurA binding in vitro and pfurA regulation upon oxidative-stress in M . smegmatis were abolished . Thus, pfurA is an oxidative stress-responsive promoter controlled by the FurA protein .
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