Inductors and regulatory properties of the genomic island‐associated fru 2 metabolic operon of Streptococcus agalactiae

Summary The fru 2 metabolic operon of Streptococcus agalactiae encodes the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) enzyme II complex Fru 2 (EIIB Fru2 , EIIA Fru2 , and EIIC Fru2 ); Fru 2 R, a transcriptional activator with PTS regulatory domains (PRDs); a d ‐allulose‐6‐phosphate 3‐epimerase; a transaldolase; and a transketolase. We showed that the transcription of fru 2 is induced during the stationary phase of growth in complex media and during incubation in human cerebrospinal or amniotic fluids. d ‐allose and d ‐ribose are environmental signals governing this induction. PTS Fru2 is involved in the activation of the fru 2 promoter, and the histidine‐67 of EIIA Fru2 and the cysteine‐9 of EIIB Fru2 are important for this function. The activation of fru 2 is also controlled by Fru 2 R. The histidine‐243 in the PRD 1 domain, the histidine‐323 in the PRD 2 domain, the cysteine‐400 in the EIIB‐like domain, and the histidine‐549 in the EIIA‐like domain are important for the function of Fru 2 R. Fru 2 R binds to a DNA region containing palindromic sequences upstream of the identified transcriptional start site. EIIB Fru2 interacts physically with the C‐terminal part of Fru 2 R (expressing the EIIB‐like and EIIA‐like motifs) and with EIIA Fru2 . We propose a model of regulation of fru 2 depending on the presence of an activatory carbohydrate in the growth medium.