Structural and Functional Characterization of the Tripartite Tricarboxylate Transport System BctCBA of Bordetella pertussis

• Grant number: 24/20003-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: March 01, 2025
• End date: February 28, 2029
• Field of knowledge: Biological Sciences - Biochemistry - Chemistry of Macromolecules
• Principal Investigator: Leonardo Talachia Rosa
• Grantee: Natalia Fernanda Bueno
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 22/11936-6 - The Tripartite Tricarboxylate Transporter (TTT) family: investigating signalling and transport networks in the re-emerging pathogen Bordetella pertussis, AP.JP

Abstract

Whooping cough, a respiratory disease caused by the Gram-negative bacterium Bordetella pertussis, poses a serious threat to unvaccinated infants and young children, leading to severe respiratory complications and, in many cases, death. Despite the initiation of vaccination efforts in 1940, which have achieved nearly 85% global coverage, the disease still accounts for approximately 24 million cases annually, resulting in around 160,000 deaths among children under five years of age.Bordetella pertussis has strict nutritional requirements; its primary source of carbon is exclusively amino acids, as it cannot metabolize monosaccharides due to the absence of certain enzymes essential for the initial reactions of the glycolytic pathway. To ensure its survival, the bacterium employs highly efficient nutrient transport systems, particularly the BctCBA system, which belongs to the family of Tripartite Tricarboxylate Transporters (TTT). This system has a translocation channel formed by the transmembrane proteins BctB and BctA, while BctC acts as the Solute Binding Protein (SBP). According to the literature, the primary biological function of this transport system is the uptake of citrate, a vital component of the citric acid cycle and its associated anaplerotic reactions. Current studies and structural analyses conducted using Alphafold2 suggest that the BctCBA complex transports citrate through an "elevator" mechanism, wherein the substrate is moved through the channel via cyclic movements. This mechanism allows the substrate binding site to be alternately exposed to the cytoplasmic and periplasmic sides of the membrane, thereby facilitating efficient citrate uptake even at low concentrations.The proposed project aims to elucidate the mechanism of citrate translocation through the BctCBA system using Cryo-electron Microscopy (Cryo-EM). This study seeks to describe and deepen our understanding of the interactions between the domains of the protein complex and the substrate, contributing to the identification of potential targets for future therapeutic research focused on disease control