RESUMO
The genome of the facultative anaerobic thermoacidophilic archaeon Thermoplasma volcanium contains the open-reading frames (ORFs) tvsod and tvogg, which are predicted to encode a putative superoxide dismutase and an 8-oxoguanine DNA glycosylase, respectively. Tvsod is immediately upstream of tvogg, and these two ORFs are aligned in a head-to-tail manner in a single operon. A previous study showed that T. volcanium contains an ORF (TVN0292) encoding the ferric uptake regulator (Fur) and that the T. volcanium Fur protein (TvFur) binds to its own promoter in a metal-dependent manner in vitro. Here, we demonstrated that TvFur also binds to the tvsod-tvogg promoter and determined the TvFur-binding sequences in the tvsod-tvogg promoter by DNaseI footprinting analysis. These results suggest that Fur is required for resistance against reactive oxygen species in this facultative anaerobic archaeon.
Assuntos
Proteínas de Bactérias/genética , Genes Bacterianos , Óperon , Estresse Oxidativo/genética , Regiões Promotoras Genéticas , Proteínas Repressoras/genética , Thermoplasma/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Sítios de Ligação , Dados de Sequência Molecular , Fases de Leitura Aberta , Proteínas Repressoras/metabolismo , Thermoplasma/metabolismoRESUMO
Because archaea possess many respiratory enzymes or radical scavengers with catalytic domains that contain iron, the expression of the genes encoding these enzymes might be regulated by iron acquisition. The genome of an archaeon, Thermoplasma volcanium contains a gene that encodes Fur (TVN0292). The fur gene of T. volcanium was amplified by PCR, and cloned into plasmid pET28a. TvFur (T. volcanium Fur protein) was expressed in E. coli cells and then purified. EMSA revealed that TvFur binds to its own promoter DNA. The binding to its own promoter was in an Mn(2+)-, Zn(2+)-, and Ni(2+)-dependent manner. DNase I footprinting analysis revealed that the binding sequence of tvfur promoter was 5'-G TTATTAT G TTTATAT A TTAATTA G-3'. An analysis utilizing oligonucleotides in TvFur-binding sequences revealed that TvFur binds to the TATA-box or regions in the vicinity of the TATA-box in the promoter. These results indicated that TvFur regulates transcription depending on the availability of environmental divalent cations.
