Part of the ABC transporter complex TcyJKLMN involved in L-cystine import. Responsible for energy coupling to the transport system (Probable). Is also involved in cystathionine, djenkolate, and S-methylcysteine transport. The complex is composed of two ATP-binding proteins (TcyN), two transmembrane proteins (TcyL and TcyM) and two solute-binding proteins (TcyJ and TcyK). More strongly expressed in the presence of methionine than in the presence of sulfate. Belongs to the ABC transporter superfamily. L-cystine importer (TC 3.A.1.3.13) family.