Silicon and Aquaporins
Aquaporins or major intrinsic proteins (MIPs) are transmembrane channel proteins, which facilitate the passive and bidirectional diffusion of water and a variety of small and noncharged compounds across biological membranes. MIPs are found in organisms of all kingdoms of life and are present in all main subcellular membrane systems. The substrate specificity/spectra of aquaporins are highly isoform-dependent. Certain isoforms of plants were shown to facilitate the transmembrane diffusion of the metalloid silicic acid, a derivative of silicon. All organisms face the challenge to handle considerable variations in the concentration of metalloids to which they are exposed to. This happens when facing the demand to acquire sufficient amounts for their metabolism or, conversely, the necessity to extrude them to prevent toxicity. This is achieved through homeostatic...