Probable subunit of an amino acid transporter involved in the regulation of the amino acid metabolism. Stimulates amino acid export by activating nonselective amino acid facilitators. Expressed in the vascular tissues, even in the minor veins of the leaves. The VIMAG motif is necessary for the function of the protein. Overexpression of GLUTAMINE DUMPER 4 leads to free amino acid levels accumulation (Ref.7, PubMed:20018597). Belongs to the GLUTAMINE DUMPER 1 (TC 9.B.60) family.