Characterisation of Escherichia coli TatA

RODRIGUEZ FERNANDA; JASON SCHNELL; BEN BERKS

Santa Margherita di Pula, Sardinia

Conferencia; PROTEIN TRANSPORT SYSTEMS (EMBO meeting); 2011

EMBO

The twin-arginine translocation (Tat) pathway has the remarkable ability of translocating folded proteins across membranes. This poses the mechanistic challenge of maintaining the membrane permeability barrier to ions while providing a pathway across the membrane for much larger proteins that differ widely in size, shape, and surface properties. The Tat pathway is present in bacteria, archaea, and chloroplasts. In Escherichia coli the Tat translocase consists of three membrane proteins: TatA, TatB and TatC. Experimental evidence suggests that a TatBC complex binds to the signal peptide of the substrate protein. This binding event triggers the assembly of TatA with the TatBC-substrate complex, and the substrate protein is then translocated probably via TatA. The TatA protein is predicted to have an N-terminal transmembrane alfa-helix, followed by an amphipathic helix and an unstructured C-terminal region. TatA is currently considered to form tetramers which act as building blocks for the higher order oligomers that mediate transport. The higher order polymerisation of TatA is dynamic and thought to be biased by substrate-bound TatBC. Unfortunately, very few molecular-level details of the transport process are known and there is currently no real understanding of how transport occurs. In this work we report the results of structural studies by NMR spectroscopy performed on E. coli TatA aimed at unveiling its molecular mechanism of action.