ATOMIC-FORCE MICROSCOPY PROPOSES A NOVEL MODEL FOR STEM-LOOP STRUCTURE THAT BINDS A HEAT-SHOCK PROTEIN IN THE STAPHYLOCOCCUS-AUREUS HSP70 OPERON

The Staphylococcus aureus HSP70 operon produces a polycistronic RNA in response to heat shock, and ORF37 is the first protein to be translat ed. The promoter of this operon contains a palindromic nucleotide sequ ence that may form a stem-loop structure. Structural analysis of the p romoter regions by atomic force microscopy (AFM) revealed a quadruplet that consists of a pair of stem-loops. A novel 'SL2S' (Stem-Loop-Loop -Stem) model was proposed for this structure. AFM also revealed the bi nding of ORF37 to the quadruplet, establishing a molecular mechanism f or this heat shock gene expression; ORF37 acts as a regulator by bindi ng to the SL2S structure in the promoter. (C) 1996 Academic Press, Inc .