Aquaglyceroporins: ancient channels for metalloids

Abstract

The identification of aquaglyceroporins as uptake channels for arsenic and antimony shows how these toxic elements can enter the food chain, and suggests that food plants could be genetically modified to exclude arsenic while still accumulating boron and silicon.

Figure 1

Periodic table of the metalloids. Metalloid substrates of aquaglyceroporins are shown both in their position in the periodic table and as molecular models. The size of each metalloid is shown in scale relative to glycerol (right). Atomic coordinates from the Cambridge Structural Database [16] were modeled with InsightII to calculate partial charges (blue, positive; red, negative; green and yellow reflect intermediate charges between blue and red) and plotted with PyMol. Beside each metalloid is listed its transport proteins. Each is a NIP except for Lsi2, which is an ArsB homolog. Species abbreviations: At, Arabidopsis thaliana; Lj, Lotus japonicus; Os, Oryza sativa; Zm, Zea mays.

Figure 2

Structures of SoPIP2;1 and GlpF. (a) Model of the spinach SoPIP2;1 water channel structure (Protein Data Bank (PDB) entry 1Z98), showing water molecules passing through the channel (red spheres). (b) Model of the E. coli GlpF glycerol channel (PDB 1LDI) showing water molecules passing through the channel (red spheres). In each structure, the amino-terminal half is in green and the carboxy-terminal half is in purple. (c, d) Cross-sectional views of SoPIP2;1 and GlpF, showing the narrowest opening of the pore with a water or glycerol molecule, respectively.