Novel molecules of the multi-drug and toxin efflux (MATE) family of molecules, designated herein as mutant ferric reductase defective (FRD3) nucleic acid and protein molecules are disclosed. The FRD3 nucleic acid and protein molecules are useful as modulating agents in regulating metal homeostasis, e.g., iron homeostasis. The invention further describes transgenic plants in which expression of a FRD3 polypeptide of the invention is altered. Compositions containing FRD3 molecules and methods of using such molecules are also provided.