Part of the twin-arginine translocation (Tat) system that transports large folded proteins containing a characteristic twin-arginine motif in their signal peptide across membranes. TatA could form the protein-conducting channel of the Tat system (Probable). Forms a complex with TatC (By similarity). Cytoplasmic and membrane-bound TatA form high-molecular-weight complexes. H.volcanii possesses two TatA translocases: TatAo and TatAt. Each may interact with specific Tat substrates (PubMed:16291683). Belongs to the TatA/E family.