Summary of point mutant phenotypes. A diagram of the IRT1 amino acid
sequence is shown with predicted transmembrane domains in the center,
numbered I–VIII, predicted cytoplasmic loops above, and predicted
extracellular regions below. Residues shaded in pink (Glu-103) are
those whose replacement with alanine leads to variants that transport
Fe, Mn, and Cd but not Zn; those in blue (Asp-100) are residues whose
replacement with alanine leads to variants that transport Zn and Cd but
not Fe and Mn, and those in green (Asp-136) transport Zn and reduced
levels of Cd. Residues whose replacement with alanine leads to variants
with no transport activity are shown in gray (His-96, His-197, Ser-198,
His-224, and Glu-228), and those with wild-type transport function are
shown in gold (Cys-109, Tyr-295, Asp-300, and Glu-305).