title: ABC Transporter CslAB, a Stabilizer of ComCDE Signal in Streptococcus mutans.
abstract: BACKGROUND
  In Streptococcus mutans, ComCDE, a peptide-induced two-component signal transduction system, forms a closed signal transduction, and even if difunctional ComE closes this signal at its headstream to avoid its infinite amplification, it is not enough for ComE to work in a concentration-dependent manner. CslAB has a chance to regulate ComCDE by controlling extracellular competence-stimulating peptide (CSP) concentration through its processing and secretion.
  
  
  OBJECTIVE
  To first confirm the binding properties of cslAB promoter (PcslAB) with ComE, then to uncover in vivo need of cslAB expression, and finally to unveil the role of CslAB.
  
  
  METHODS
  Electrophoretic mobility shift assay was used to confirm the binding properties of PcslAB with ComE. In vivo cslAB transcription was detected by β-galactosidase activity because its gene has been fused to cslAB operon, and finally the role of CslAB was reviewed.
  
  
  RESULTS
  PcslAB is a weak promoter responding to ComE and its binding appears to be negative cooperative. Although PcslAB is partially controlled by ComCDE, it can respond to ComCDE regulation. Supported by the obtained molecular evidence, CslAB acts as a stabilizer of ComCDE signal on the patterns of its expression.
  
  
  CONCLUSIONS
  PcslAB is partially controlled by ComCDE. CslAB is a stabilizer of ComCDE signal to ensure that ComE works in a concentration-dependent manner.
authors.affiliation: Department of Biotechnology, School of Food and Bioengineering, Jiangsu University, Zhenjiang, China.
authors.forename: Tianlei
authors.initials: T
authors.lastname: Liu
authors.affiliation: The First People's Hospital of Lanzhou City, Lanzhou, China.
authors.forename: Shoubin
authors.initials: S
authors.lastname: Xue
authors.affiliation: Department of Biotechnology, School of Food and Bioengineering, Jiangsu University, Zhenjiang, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
keywords: ComCDE;; CslAB; Electrophoretic Mobility Shift Assay; Streptococcus mutans; Two Component Signal Transduction System