Proton-linked monocarboxylate transporter. It catalyzes the transport of pyruvate across the plasma membrane. Probably involved in hepatic lipid metabolism: overexpression results in an increase of triacylglycerol(TAG) levels, small increases in intracellular diacylglycerols and decreases in lysophosphatidylcholine, cholesterol ester and sphingomyelin lipids. H(+)(out) + pyruvate(out) = H(+)(in) + pyruvate(in) Interacts with isoform 2 of BSG. Belongs to the major facilitator superfamily. Monocarboxylate porter (TC 2.A.1.13) family.