The twin-arginine translocation (Tat) protein export pathway

Abstract

The twin-arginine translocation (Tat) protein export system is present in the cytoplasmic membranes of most bacteria and archaea and has the highly unusual property of transporting fully folded proteins. The system must therefore provide a transmembrane pathway that is large enough to allow the passage of structured macromolecular substrates of different sizes but that maintains the impermeability of the membrane to ions. In the Gram-negative bacterium Escherichia coli, this complex task can be achieved by using only three small membrane proteins: TatA, TatB and TatC. In this Review, we summarize recent advances in our understanding of how this remarkable machine operates.

Copper-responsive gene regulation in bacteria

“…Although MCOs function in the periplasm, there is no apparent preference for CusRS systems, which sense periplasmic copper concentrations, over CueR sensors, which respond to the cytoplasmic copper status. It is worth noting that the copper-inducible MCO in the Gram-positive bacterium C. glutamicum contains a cysteine residue, thought to serve as a lipid anchor, immediately downstream of the signal peptide cleavage site (Palmer & Berks, 2012;Schelder et al, 2011).…”

Plant mitochondria contain the protein translocase subunits TatB and TatC

“…It is named after its targeting signal, which contains a pair of adjacent arginine residues (the twin arginines). Identified in all domains of life, Tat pathways play essential roles in a number of different cellular processes including: bacterial pathogen virulence, cell separation, phosphate and iron metabolism, photosynthetic and respiratory metabolism (Berks, 2015;Palmer and Berks, 2012).…”

Live cell imaging shows reversible assembly of the TatA component of the twin-arginine protein transport system

“…The Sec (secretion) pathway threads unstructured proteins across the membrane through an aqueous channel (1), whereas the Tat (twin-arginine translocation) pathway transports folded proteins using a currently uncharacterized mechanism (2,3). The Tat transport system has the greater mechanistic challenge, not only because folded proteins require a wider transport pathway, but because proteins have very different sizes and shapes when folded making it difficult to seal tightly around the protein during transport.…”