Table 2.
As(III) and Sb(III) transporting aquaporin homologs, comparison of the constriction region and summary of transport properties
| AQP | R1 | R2 | R3 | R4 | As(III) influx | As(III) efflux | Sb(III) influx | Reference |
| AtNIP1;1 | W | V | A | R | - | - | - | This study |
| AtNIP2;1 | W | V | A | R | - | - | - | This study |
| OsNIP1;1 | W | V | A | R | - | - | - | This study |
| AtNIP5;1 | A | I | G | R | •• | ••• | • | This study |
| AtNIP6;1 | A | I | A | R | •• | ••• | • | This study |
| AtNIP7;1 | A | V | G | R | • | - | ••• | This study |
| OsNIP2:1 | G | S | G | R | ••• | ••• | ••• | This study |
| OsNIP2:2 | G | S | G | R | • | - | • | This study |
| OsNIP3;2 | A | A | A | R | ••• | •• | •• | This study |
| LjNIP5;1 | A | I | G | R | •• | • | •• | This study |
| LjNIP6;1 | T | I | A | R | ••• | ••• | ••• | This study |
| rAQP9 | F | S | C | R | ••• /+ | • /nd | ••• /+ | This study /[26] |
| ScFps1 | W | N | T | R | • /+ | - /nd | • /+ | This study /[24] |
| hAQP9 | F | A | C | R | + | nd | nd | [53] |
| hAQP7 | F | G | Y | R | + | nd | nd | [53] |
| EcGlpF | W | G | F | R | + | nd | + | [65,66] |
| SmAqpS | T | A | S | V | + | + | + | [56] |
Aquaporin (AQP) homologs tested for transport of arsenite and antimonite. The tetrad of amino acids from transmembrane helix 2 (R1), transmembrane helix 5 (R2), and 2 residues from loop E (R3 and R4) that constitutes the selective filter are displayed. The abilities to channel the influx or efflux of arsenite or influx of antimonite of the tested aquaporins in various growth and transport assays are ranked (nd, not determined; +, transport; -, no transport and from • weakest to ••• best transport).