MRP5 (190-200 kDa) is closely related to MRP4, both lacking the first five membrane spanning regions. MRP5 is a GS-X multi specific organic anion pump (nucleotide analogs). MRP5 may transport DNP-GS and may be inhibited by certain inhibitors of organic anion transport (sulfinpyrazone). MRP5 may also transport organic anions with the anionic moiety of phosphate/phosphonate group, a function which provides the ability to resist against anti cancer drugs 6-MP and thioguanine as well as the anti-HIV drug PMEA.