Inductors and regulatory properties of the genomic island-associated fru sub(2) metabolic operon of Streptococcus agalactiae

• Published in: Molecular microbiology Vol. 103; no. 4; pp. 678 - 697
• Main Authors: Patron, Kevin, Gilot, Philippe, Rong, Vanessa, Hiron, Aurelia, Mereghetti, Laurent, Camiade, Emilie
• Format: Journal Article
• Language: English
• Published: 01.02.2017
• Subjects: Streptococcus agalactiae
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.13581

The fru sub(2) metabolic operon of Streptococcus agalactiae encodes the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) enzyme II complex Fru sub(2) (EIIB super(Fru2), EIIA super(Fru2), and EIIC super(Fru2)); Fru sub(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 sub(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 super(Fru2) is involved in the activation of the fru sub(2) promoter, and the histidine-67 of EIIA super(Fru2) and the cysteine-9 of EIIB super(Fru2) are important for this function. The activation of fru sub(2) is also controlled by Fru sub(2)R. The histidine-243 in the PRD sub(1) domain, the histidine-323 in the PRD sub(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 sub(2)R. Fru sub(2)R binds to a DNA region containing palindromic sequences upstream of the identified transcriptional start site. EIIB super(Fru2) interacts physically with the C-terminal part of Fru sub(2)R (expressing the EIIB-like and EIIA-like motifs) and with EIIA super(Fru2). We propose a model of regulation of fru sub(2) depending on the presence of an activatory carbohydrate in the growth medium. The regulation mechanism of the fru sub(2) operon of Streptococcus agalactiae was enlightened by (i) localizing its transcriptional promoter and identifying carbohydrate inductors (ii) determining the DNA binding region of its regulator (Fru sub(2)R), (iii) identifying histidine or cysteine residues affecting the function of the encoded sugar transporter (PTS super(Fru2)) and regulator (Fru sub(2)R), and (iv) revealing physical interactions between PTS super(Fru2) and Fru sub(2)R.