Helical wheel representation of predicted TMD4 of Nramp1 and Nramp2. The structure of TMD4 of both Nramp1 and Nramp2 is represented as a helical wheel. The Nramp2 residue is given first when amino acid differences exist between Nramp1 and Nramp2. The positions of the G185R Nramp2 mutation in mk mice and the G169D Nramp1 mutation in bcg mice (corresponding to G184 in Nramp2) are shown. G185 is indicated with a gray circle and D192, which lies close to G185 in this projection, is indicated with a black circle.