The tatC gene cluster is essential for viability in halophilic archaea

In prokaryotes the twin-arginine translocase (Tat) is a unique transport system for the export of folded proteins. The Tat pathway is usually involved in the export of a small proportion of extracytoplasmic proteins. An exception is found in halophilic archaea, in which the majority of secretory proteins have been predicted to be Tat-dependent. All haloarchaea analysed to date contain two genes encoding homologues of the Tat-component TatC. In all of these cases both genes are located adjacently on the chromosome, indicating that they form a functional unit. We show that this gene cluster is essential for viability in haloarchaea, which is in complete contrast to all other prokaryotes that have been tested thus far.