Sulerythrin, the smallest member of the rubrerythrin family, from a strictly aerobic and thermoacidophilic archaeon, Sulfolobus tokodaii strain 7

Abstract

A protein corresponding to the N-terminal domain of rubrerythrin was isolated from a strictly aerobic archaeon, Sulfolobus tokodaii strain 7. The molecular mass was found to be 15.8 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, 16 278 Da by time-of-flight mass spectrometry and 34.5 kDa by gel filtration chromatography, suggesting that the protein is dimeric. Two mol iron and 1–2 mol zinc mol −1 protein were detected. On addition of the azide ion, the absorption spectrum was greatly affected. The far UV circular dichroism spectrum suggested that the protein was mostly composed of α-helices. The N-terminal sequence completely matched the open reading frame, st2370, recently found on genome analysis of the organism. The protein was homologous to rubrerythrin but lacked a C-terminal rubredoxin domain. It was found in the genus Sulfolobus and therefore named sulerythrin; it is the smallest and first aerobic member of the rubrerythrin family.