The GS-X Pump in Plant, Yeast, and Animal Cells: Structure, Function, and Gene Expression

This review addresses the recent molecular identification of several members of the glutathione S-conjugate (GS-X) pump family, a new class of ATP-binding cassette (ABC) transporters responsible for the elimination and/or sequestration of pharmacologically and agronomically important compounds in mammalian, yeast and plant cells. The molecular structure and function of GS-X pumps encoded by MRP, cMOAT, YCF1. and AtMRP genes, have been conserved throughout molecular evolution. The physiologic function of GS-X pumps is closely related with cellular detoxification, oxidative stress, inflammation, and cancer drug resistance. Coordinated expression of GS-X pump genes, e.g., MRP1 and YCF1, and γ-glutamylcystaine synthetase, a rate-limiting enzyme of cellular glutathione (GSH) biosynthesis, has been frequently observed.