Structural assessment of OsNIP2;1 highlighted critical residues defining solute specificity and functionality of NIP class aquaporins

•The free energy landscape for silicon and arsenic permeation was traced.•The transport cycle reveals novel energy constraints onsilicon and arsenic permeation.•Predicted functionally important residues were validated in yeast.•Altering conserved amino acids in loop C and loop D directly influenced metalloid uptake of OsNIP2;1.•Protein variants with lower arsenic uptake were identified to reduce arsenic levels with minimum counterproductive effects.