Mitochondrial transporter required for glutathione import into mitochondria. Glutathione, which plays key roles in oxidative metabolism, is produced exclusively in the cytosol and is imported in many organelles. Mitochondrial glutathione is required for the activity and stability of proteins containing iron-sulfur clusters, as well as erythropoiesis. Belongs to the mitochondrial carrier (TC 2.A.29) family.