AN ABNORMALLY ACIDIC TATA-BINDING PROTEIN FROM A HYPERTHERMOPHILIC ARCHAEON

The gene encoding the TATA-binding protein (PkTBP) from a hyperthermop hilic archaeon, Pyrococcus sp, KOD1 (Pk), was cloned and sequenced. An open reading frame with homology to the conserved C-terminal core reg ion of eukaryotic TBP was expressed in Escherichia coli. Specific DNA- binding activity of the recombinant PkTBP (190 amino acids, 21.36 kDa) was also demonstrated, Although it was composed of a structurally dir ect repeat sequence which is similar to eukaryotic TBP, the total net charge of archaeal TBP was amazingly negative (calculated isoelectric point (pI) was 4.66 and experimentally estimated pi was 4.8). A series of five Glu residues was found at the C terminus of archaeal TBP. The se data strongly suggest that a positively charged protein is also inv olved in the transcription initiation event which might stabilize the structure of the genomic DNA under high-growth-temperature conditions.