eLife assessment
This study provides valuable insight into the diversity within the NRAMP superfamily of transporters. Evidence of divalent metal ion transport and the structure (obtained without added metal ions) are convincing. However, molecular insight into Al3+ recognition and transport is incomplete, and the work would be strengthened by the determination of a metal-bound structure or additional experiments (such as molecular dynamics simulations or quantitative Al3+ binding/transport assays) to support the proposed Al3+ binding site. The work will be of interest to structural biologists and biophysicists studying NRAMP transporters.