Fig. 2. Secretion through the Tat pathway.

Bacteria secrete folded proteins across the cytoplasmic membrane using the Tat secretion pathway. This pathway consists of 2–3 components (TatA, TatB, and TatC). In Gram-negative bacteria, TatB and TatC bind a specific N-terminal signal peptide containing a “twin” arginine motif on folded Tat secretion substrates. TatB and TatC then recruit TatA to the cytoplasmic membrane, where it forms a channel. Folded proteins are then translocated across the channel and into the periplasm. In Gram-negative bacteria, these proteins may remain in the periplasm, or can be exported out of the cell by the T2SS.