Regulatory elements of the raffinose operon: nucleotide sequences of operator and repressor genes.
The raffinose (raf) operon is negatively controlled by the specific binding of raf repressor (rafR gene) to raf operator (rafO) DNA. Both rafR and rafO have been sequenced. The 1,011-base-pair rafR gene encodes a 336-amino-acid polypeptide containing an N-terminal helix-turn-helix motif. rafO, as defined by in vivo titration of raf repressor, consists of two nearly identical 18-base-pair palindromes that flank the -35 box of the raf promoter.