A subgroup of plant aquaporins facilitate the bi-directional diffusion of As(OH)3 and Sb(OH)3across membranes

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).

ISSN: 1741-7007