Inductors and regulatory properties of the genomic island-associated fru2 metabolic operon of Streptococcus agalactiae

SUMMARY The fru2 metabolic operon of Streptococcus agalactiae encodes the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) enzyme II complex Fru2 (EIIBFru2, EIIAFru2, and EIICFru2); Fru2R, 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 fru2 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. PTSFru2 is involved in the activation of the fru2 promoter, and the histidine-67 of EIIAFru2 and the cysteine-9 of EIIBFru2 are important for this function. The activation of fru2 is also controlled by Fru2R. The histidine-243 in the PRD1 domain, the histidine-323 in the PRD2 domain, the cysteine-400 in the EIIB-like domain, and the histidine-549 in the EIIA-like domain are important for the function of Fru2R. Fru2R binds to a DNA region containing palindromic sequences upstream of the identified transcriptional start site. EIIBFru2 interacts physically with the C-terminal part of Fru2R (expressing the EIIB-like and EIIA-like motifs) and with EIIAFru2. We propose a model of regulation of fru2 depending on the presence of an activatory carbohydrate in the growth medium. This article is protected by copyright. All rights reserved.