The Periplasmic Binding Protein of a Tripartite Tricarboxylate Transporter is Involved in Signal Transduction

• Published in: Journal of molecular biology 2005-08, Vol.351 (4), p.799-809
• Main Authors: Antoine, Rudy, Huvent, Isabelle, Chemlal, Karim, Deray, Isabelle, Raze, Dominique, Locht, Camille, Jacob-Dubuisson, Françoise
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Base Sequence; Bordetella pertussis; Bordetella pertussis - drug effects; Bordetella pertussis - genetics; Bordetella pertussis - metabolism; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Citric Acid - pharmacology; DNA, Bacterial - genetics; Lac Operon; Models, Biological; Operon - drug effects; periplasmic binding protein; Periplasmic Binding Proteins - chemistry; Periplasmic Binding Proteins - genetics; Periplasmic Binding Proteins - metabolism; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Signal Transduction; tripartite tricarboxylate transporter (TTT); two-component system; Two-Hybrid System Techniques
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2005.05.071

A new type of solute importer has been identified recently in various bacterial genera and called the tripartite tricarboxylate transporter (TTT). TTTs consist of two cytoplasmic membrane proteins and a periplasmic solute-binding protein. In the whooping cough agent Bordetella pertussis, a TTT system that has been called BctCBA mediates the uptake of citrate, with BctA and BctB being the membrane components and BctC, the periplasmic protein. Here, we describe that the expression of the bctCBA operon is induced by the presence of citrate in the milieu. The signalling cascade involves both BctC and the signal transduction two-component system BctDE, encoded by an operon adjacent to bctCBA. Furthermore, two-hybrid analyses and affinity chromatography experiments indicated that citrate-liganded BctC interacts with the periplasmic domain of the sensor protein, BctE. Thus, BctC is part of the signalling cascade leading to upregulation of the transporter operon in the presence of its solute, a new function for periplasmic binding proteins of TT transporters.