The archaeal twin-arginine translocation pathway

Abstract

The twin-arginine translocation (Tat) pathway is a system with the unique ability to export proteins in a fully folded conformation. Its main components are TatA, TatB and TatC, all of which are required for Tat-dependent export. The Tat pathway is found in several Archaea, and in most of them a moderate number of predicted Tat-dependent substrates are present. Putative substrates include those binding cofactors such as iron–sulphur clusters and molybdopterin. In these Archaea, the role of the Tat pathway seems to be similar to that of bacteria: the export of a small subset of proteins that fold before translocation across the cytoplasmic membrane. The exception to this is the Tat system of the halophilic archaeon Halobacterium sp. NRC-1. In this organism, the majority of extra-cytoplasmic proteins are predicted to use the Tat pathway, which is, most likely, a specific adaptation to its particular lifestyle in highly saline conditions.