Primary solute translocator for anionic substances; particularly it is a free sialic acid transporter in the lysosomes (Probable). Receptor for CM101, a polysaccharide produced by group B Streptococcus with antipathoangiogenic properties. Significantly expressed in lung endothelial cells, and much less in liver. Belongs to the major facilitator superfamily. Sodium/anion cotransporter family.