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. Required for YwbN secretion. Forms a complex with TatCy. Two types of complexes exist: one composed of TatAy and TatCy, and another composed only of TatAy. Cytosolic TatA forms large complexes or aggregates. B.subtilis possesses two minimal, substrate-specific, Tat translocases: TatAd-TatCd and TatAy-TatCy, each one composed of a TatA and a TatC protein. TatA is bifunctional and performs the function of both the TatA and TatB proteins of Gram-negative organisms. Belongs to the TatA/E family.