The Bacterial Twin-Arginine Translocation Pathway

Abstract

The twin-arginine translocation (Tat) pathway is responsible for the export of folded proteins across the cytoplasmic membrane of bacteria. Substrates for the Tat pathway include redox enzymes requiring cofactor insertion in the cytoplasm, multimeric proteins that have to assemble into a complex prior to export, certain membrane proteins, and proteins whose folding is incompatible with Sec export. These proteins are involved in a diverse range of cellular activities including anaerobic metabolism, cell envelope biogenesis, metal acquisition and detoxification, and virulence. The Escherichia coli translocase consists of the TatA, TatB, and TatC proteins, but little is known about the precise sequence of events that leads to protein translocation, the energetic requirements, or the mechanism that prevents the export of misfolded proteins. Owing to the unique characteristics of the pathway, it holds promise for biotechnological applications.

Functional analysis of a Campylobacter jejuni alkaline phosphatase secreted via the Tat export machinery

“…A search of the C. jejuni proteome for putative Tat substrates based on the presence of the specific Tat recognition consensus sequence (RRxFLK) (Lee et al, 2006) indicated 11 potential Tat substrates (Table 3) (Dilks et al, 2003), including NapA. In other bacterial species this Tat substrate reduces nitrate to nitrite, which may be used by the bacterium as an alternative electron acceptor The pH optimum of PhoA Cj activity was determined after lysis of C. jejuni 81116 in buffer of the indicated pH using PNPP as substrate.…”

The role of protein secretion systems in the virulence of the intracellular pathogen Legionella pneumophila

“…The Tat system, in contrast to the Sec system, allows transport of folded proteins that have the typical characteristic of bearing two arginine residues in their signal peptide. The exact mechanism of Tat transport is not fully determined yet but a complex of TatB and TatC proteins probably recognizes the Tat substrate, followed by transport through a pore consisting of multiple TatA proteins (reviewed by Lee et al, 2006;see Fig. 1).…”

Plant mitochondria contain the protein translocase subunits TatB and TatC

“…The twin-arginine translocation (Tat) pathway differs from most other protein translocating systems in that it transports fully folded proteins (Lee et al, 2006). It is named after its targeting signal, which contains a pair of adjacent arginine residues (the twin arginines).…”