Identification of the Docking Regions within the TatBC Receptor of the Twin­‐Arginine Translocation System for the Redox Enzyme Maturation Protein Chaperones in Escherichia coli

Abstract

The Twin-arginine translocation pathway (Tat) serves for targeting and translocation of fully folded proteins across cytoplasmic membranes in bacterial and plant chloroplast thylakoid membranes. In Escherichia coli there are three core components of the Tat system: TatA, TatB, and TatC, where TatB and TatC subunits form the receptor complex for Tat-bound proteins and TatA monomers form the translocation pore itself. Redox Enzyme Maturation Proteins (REMPs) are system specific chaperones, which play significant roles in the maturation of Tat dependent respiratory enzymes. DmsD chaperone – the REMP for dimethyl sulfoxide reductase in E. coli – is known to interact with TatBC complex from previous research. Here in vivo and in vitro techniques were used to investigate interactions between REMPs and the cytoplasmic domains of TatBC proteins. Ten REMPs from E. coli were screened for in vivo interactions with the TatBC using Bacterial adenylate cyclase two-hybrid assay, the results demonstrated that all but the formate dehydrogenase REMPs play a crucial role in targeting the substrates - respiratory enzymes - to the Tat system. In vitro peptide assay and Isothermal titration calorimetry was then implemented in order to determine the regions within TatB and TaC, responsible for the REMPs docking.