The twin-arginine translocation (Tat) protein export system transports folded proteins across the cytoplasmic membrane of bacteria and the thylakoid membrane of chloroplasts. Substrates, targeted to this system via signal peptides containing a characteristic twin-arginine motif, are first recognized by a membrane protein receptor complex formed from TatB and TatC. While atomic structures for each individual subunit have recently been determined, the TatBC substrate receptor complex has eluded structural determination. Here we adopt the use of single-particle cryo-electron microscopy (cryo-EM) towards this goal. To overcome particle alignment issues commonly attributed to integral membrane proteins, TatCs having large extramembranous domains were identified bioinformatically. Recombinant TatBC complexes from Nitratifractor salsuginis, Myxococcus xanthus, and Cystobacter violaceus were purified to homogeneity. Multiangle light scattering analyses (MALS) suggested these complexes were formed from three copies of each subunit. Structures of these TatC extramembranous domains were solved by X-ray crystallography. These entirely helical domains form homotrimers and can be docked into a negative stain electron microscopy reconstruction of the M. xanthus TatBC complex. Having identified optimal conditions for grid preparation, cryo-EM data is now being collected and processed with the aim of yielding high-resolution reconstructions of the TatBC substrate receptor complex. A structural understanding of TatBC will provide novel insight into the molecular mechanism of this dynamic and unique protein export pathway.