The present invention features fully soluble and functional single-chain T-cell receptor proteins. In one aspect, the invention features soluble fusion proteins comprising an immunoglobin light chain constant region or fragment thereof covalently linked to a single-chain T-cell receptor, wherein the single-chain T-cell receptor comprises a V-α chain covalently linked to a V-β chain by a peptide linker sequence. The single-chain T-cell receptor proteins have a variety of uses including use in screens to detect cells expressly desired MHC-peptide complexes.