Proton-coupled monocarboxylate symporter. Catalyzes the rapid transport across the plasma membrane of monocarboxylates such as L-lactate, pyruvate and ketone bodies, acetoacetate, beta-hydroxybutyrate and acetate (PubMed:32415067, PubMed:9786900). Dimerization is functionally required and both subunits work cooperatively in transporting substrate (PubMed:32415067).
