Part of the twin-arginine translocation (Tat) system that transports large folded proteins containing a characteristic twin-arginine motif in their signal peptide across the thylakoid membrane. Involved in delta pH-dependent protein transport required for chloroplast development, especially thylakoid membrane formation. TATC and TATB mediate precursor recognition, whereas TATA facilitates translocation. In thylakoid membranes, TATC and TATB form a large receptor complex, containing about eight TATC-TATB pairs, which binds the precursor protein. Twin arginine signal peptide promotes pH-triggered docking of TATA oligomers to TATC-TATB receptor complex, inducing a conformational switch of TATA that results in activation of the translocase. TATA dissociates from TATC-TATB upon completion of translocation (By similarity). The C-terminus is located in the stroma. Seedling lethality after the development of three to four leaves. Non-photosynthetic mutants possess near normal pigment levels but lack one or more elements of the electron transport activity in chloroplasts. Defects in protein targeting across chloroplast thylakoid membrane (PubMed:7664731). Belongs to the TatA/E family.