Tat-fimbriae ("tafi"): An unusual type of haloarchaeal surface structure depending on the twin-arginine translocation pathway.

The surface structures of archaeal cells, many of which exist at high temperatures, high salinity, and non-physiological pH, are key factors for their adaptation to extreme living conditions. In the haloarchaeon , we have discovered a thin filamentous surface appendage called tat-fimbriae ("tafi"), which were identified to be composed of three protein subunits, TafA, TafC, and TafE, among which TafA is the major fimbrial subunit. Molecular genetic evidence demonstrates TafA was transported through the twin-arginine translocation pathway (Tat-pathway).