A Hinged Signal Peptide Hairpin Enables Tat-Dependent Protein Translocation

The Tat machinery catalyzes the transport of folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane in plants. Using fluorescence quenching and cross-linking approaches, we demonstrate that the Escherichia coli TatBC complex catalyzes insertion of a pre-SufI signal peptide hairpin that penetrates about halfway across the membrane bilayer. Analysis of 512 bacterial Tat signal peptides using secondary structure prediction and docking algorithms suggest that this hairpin interaction mode is generally conserved.

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