Sequence analysis of scrA and scrB from Streptococcus sobrinus 6715

Abstract

The complete nucleotide sequences of Streptococcus sobrinus 6715 scrA and scrB, which encode sucrosespecific enzyme II of the phosphoenolpyruvate-dependent phosphotransferase system and sucrose-6-phosphate hydrolase, respectively, have been determined. These two genes were transcribed divergently, and the initiation codons of the two open reading frames were 192 bp apart. The transcriptional initiation sites were determined by primer extension analysis, and the putative promoter regions of these two genes overlapped partially. The gene encoding enzyme IIScr, scrA, contained 1,896 nucleotides, and the molecular mass of the predicted protein was 66,529 Da. The hydropathy plot of the predicted amino acid sequence indicated that enzyme I1Scr was a relatively hydrophobic protein. The gene encoding sucrose-6-phosphate hydrolase, scrB, contained 1,437 nucleotides. The molecular mass of the predicted protein was 54,501 Da, and the encoded enzyme was hydrophilic. The predicted amino acid sequences of the two open reading frames exhibited approximately 45 and 70% identity with those encoded by scrA and scrB, respectively, from Streptococcus mutans GS5. Homology also was observed between the N-terminal region of the S. sobrinus 6715 enzyme IISr and other enzyme Ils specific for the glucopyranoside molecule, all of which generate glucopyranoside-6phosphate during translocation and phosphorylation of the respective substrates. The sequence of the C-terminal domain of the S. sobrinus 6715 enzyme IIscr shared significant homology with enzyme IIIGIc from Escherichia coli and SalmoneUa typhimurium and with the C-terminal domain of enzyme IlBg' from E. coli, indicating that the two functional domains, enzyme IIScr and enzyme IIIScr, were covalently linked as a single polypeptide in S. sobrinus 6715. The deduced amino acid sequence of the gene product of S. sobrinus scrB shared strong homology with sucrase from Bacilus subtilis, Klebsiella pneumoniae, and Vibrio alginolyticus, suggesting conservation based on the physiological roles of these proteins. * Corresponding author.ing EIIs"1 scrA, and sucrose-6-phosphate hydrolase, scrB,

The phosphoenolpyruvate:sugar phosphotransferase system of oral streptococci and its role in the control of sugar metabolism

“…Surprisingly, the sucrose 6‐phosphate hydrolase that cleaves sucrose‐6‐phosphate to yield glucose 6‐phosphate and free fructose is synthesized constitutively [86]. This is consistent with the finding that the genes encoding the EII sucrose and sucrose 6‐phosphate hydrolase are located adjacent to each other on the chromosome and transcribed divergently [16]. Sucrose is also taken up by another inducible non‐PTS transport system called Msm (Multiple sugar metabolism) [87, 88].…”

“…Following the discovery of the regulatory functions associated with the enterobacterial protein IIA Glc , studies were undertaken to determine whether Gram‐positive bacteria possessed a similar protein. IIA Glc ‐like domains were identified in the transport proteins of some Gram‐positive bacteria, such as Bacillus subtilis [14], S. mutans [15], Streptococcus sobrinus [16], Streptococcus thermophilus [17]and Clostridium acetobutylicum [18]. In B. subtilis , the IIA Glc domain is associated with the B and C domains of the II Glc complex, forming a single polypeptide [14].…”

“…The open reading frame encodes a 15.8 kDa protein that exhibits strong similarity with IIA Mtl from E. faecalis and Staphylococcus carnosus . The gene coding for the II complex involved in the transport of sucrose has been cloned and sequenced from S. mutans GS‐5 [15]and S. sobrinus 6715 [16]. The amino acid sequences of the encoded proteins are highly conserved.…”

A ComRS competence pathway in the oral pathogen Streptococcus sobrinus

“…Interestingly, we could not find a homolog of the scrA gene deleted by LeBlanc in any S. sobrinus genome. However, the reported scrA sequence [29] has >99% identity to a gene in S. ferus. We were unable to find the original NIDR 6715-10 strain used by LeBlanc, so we cannot confirm if the strain was truly S. sobrinus.…”

Characterization of the Divergent sacBK and sacAR Operons, Involved in Sucrose Utilization by Lactococcus lactis

“…Sucrose can be utilized as a sole carbon source by many bacteria, and the vast majority of bacteria take up this disaccharide via the sucrose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) (1,3,8,12,15,16). The PTS catalyzes the transport of sucrose across the cytoplasmic membrane concomitant with its phosphorylation by a sucrosespecific enzyme, enzyme II.…”