Part of the tripartite ATP-independent periplasmic (TRAP) transport system DctPQM involved in the uptake of isethionate (2-hydroxyethanesulfonate), which is then catabolized by enzymes encoded by adjacent genes in the locus. Thereby is involved in an anaerobic respiration pathway that converts the sulfonate isethionate to ammonia, acetate and sulfide. Organosulfur degradation; alkanesulfonate degradation. The complex comprises the periplasmic solute receptor protein DctP, and the fused transmembrane protein DctMQ. Cells lacking this gene lose the ability to grow with isethionate as the terminal electron acceptor. In the N-terminal section; belongs to the TRAP transporter small permease family. In the C-terminal section; belongs to the TRAP transporter large permease family.