ISOLATION AND STRUCTURE OF REPRESSOR-LIKE PROTEINS FROM THE ARCHAEON SULFOLOBUS-SOLFATARICUS - COPURIFICATION OF RNASE-A WITH SSO7C

The thermostable histone-like protein Sso7c (Sso for Salfolobus solfat aricus) from the archaeon Sulfolobus solfataricus was purified from th e supernatant of acid-soluble cell lysates. Reverse phase HPLC of an a pparently homogeneous Sso7c protein fraction from Mono S chromatograph y resulted in resolution of three further peaks. Sequence analysis rev ealed one of these components to be bovine RNase A, originating from t he culture medium and explaining the RNA hydrolyzing activities of Sso 7 preparations previously described. Sequence analysis of pure Sso7c s howed an E-Lys methylation pattern identical to that of Sso7d and a si ngle Gln --> Glu mutational difference at position 13. The remaining t wo proteins obtained after HPLC separation were identified as homologu es of bacterial repressor-like proteins, Thus, the existence of repres sor-like proteins was demonstrated at the protein level in archaea, ra ising the question of structural and functional consequences of these proteins on the otherwise eukaryotic-like basal transcriptional machin ery in archaea, (C) 1998 Federation of European Biochemical Societies.