The twin-arginine transport system: moving folded proteins across membranes

Abstract

The Tat (twin-arginine transport) pathway is a protein-targeting system dedicated to the transmembrane translocation of fully folded proteins. This system is highly prevalent in the cytoplasmic membranes of bacteria and archaea, and is also found in the thylakoid membranes of plant chloroplasts and possibly also in the inner membrane of plant mitochondria. Proteins are targeted to a membrane-embedded Tat translocase by specialized N-terminal twin-arginine signal peptides bearing an SRRXFLK amino acid motif. The genes encoding components of the Tat translocase were discovered approx. 10 years ago, and, since then, research in this area has expanded on a global scale. In this review, the key discoveries in this field are summarized, and recent studies of bacterial twin-arginine signal-peptide-binding proteins are discussed.

Novel GFP Expression Using a Short N-Terminal Polypeptide through the Defined Twin-Arginine Translocation (Tat) Pathway

“…5, lanes 4 and 5). Tat signal sequences also possess a common tripartite structure that includes a N-terminal (n-) region, a hydrophobic (h-) regions and a C-terminal (c-) region (Sargent, 2007), which is where the possible binding protein for the hydrophobic region and the apparent cleavage site of the TorA signal sequence, as well as its modified version with high hydrophilicity of the Nterminal, reduces both the GFP folding process in the cytoplasm and the translocation process of the uncleaved and cleaved target protein into the periplasm as a soluble form through the Tat pathway, as shown in Western blot and fluorescence (Fig. 5, lanes 2 and 3).…”

The Bdellovibrio bacteriovorus twin-arginine transport system has roles in predatory and prey-independent growth

“…5d) TatBCA2-optimized, and that some normally TatBCA1-specific substrates may be transported slowly, or in small amounts, by the TatBCA2 complexes in the tatA1 Bd mutant. Sequence analysis of the potential tat-substrates alone is unlikely to ever reveal which are TatBCA1-or TatBCA2-specific, as the signal peptide binds to the TatBC complex, causing a conformational change which allows either TatA1 or TatA2 to dock, creating the full transport apparatus (Sargent, 2007a).…”

“…The twin-arginine translocation (Tat) system transports folded proteins across the cytoplasmic membrane and is found in a wide variety of bacteria, whilst homologous systems are found in both archaea and eukaryotes (Sargent, 2007a;Yuan et al, 2010). Proteins transported by the Tat system in bacteria have a consensus twin arginine motif S/T-R-R-X-F-L-K (where X is any polar amino acid), a hydrophobic region and an A-x-A cleavage recognition motif in their N-terminal leading sequence (Berks, 1996;Stanley et al, 2000).…”

“…The Tat substrate is transported across the membrane via the TatA channel and released by proteolytic cleavage at the C-terminal end of the signal peptide. TatA then disassociates from the TatBC complex to reset the process Lee et al, 2006;Sargent, 2007a). Un-or mis-folded proteins are rejected then targeted for either degradation or refolding (DeLisa et al, 2002;Lee et al, 2006;Sargent, 2007a).…”

“…Proteins transported by the Tat system in bacteria have a consensus twin arginine motif S/T-R-R-X-F-L-K (where X is any polar amino acid), a hydrophobic region and an A-x-A cleavage recognition motif in their N-terminal leading sequence (Berks, 1996;Stanley et al, 2000). Tat-transported proteins are typically involved in metabolism, redox reactions, metal acquisition and cell envelope maintenance Palmer et al, 2005) and are involved in pathogenesis, symbiosis, quorum sensing and motility (Sargent, 2007a;Stevenson et al, 2007).…”