Isolated nucleic acid molecules encoding novel members of the MRT family of polypeptides which include, in a preferred embodiment, at least one transmembrane domain having at least about 30%, more preferably at least about 50%, 55%, 60%, 70%, 80% or 90% amino acid sequence identity with SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8 or SEQ ID NO:14 and/or at least one histidine rich domain, are described. The MRT polypeptides of the invention are capable of transporting metals such as Fe(II), Cd, Co, Mn, Pb, Hg and Zn. Transgenic plants in which expression of an MRT polypeptide of the invention is altered are also described. These transgenic plants can be used to remove pollutants from soil or as nutritional supplements to treat iron- or zinc-deficiency. Antisense nucleic acid molecules, recombinant expression vectors containing nucleic acid molecules of the invention, and host cells into which the expression vectors have been introduced are also described. The invention further provides isolated MRT polypeptides, fusion polypeptides and active fragments thereof. Therapeutic methods utilizing compositions of the invention are also provided.