Transcriptional factor Fur from Thermoplasma volcanium binds its own promoter DNA in a divalent cation-dependent manner

Abstract

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 Mn²⁺-, Zn²⁺-, and Ni²⁺-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.