Channel protein in tonoplast. These proteins may allow the diffusion of amino acids and/or peptides from the vacuolar compartment to the cytoplasm. Tonoplast. Found in all seed tissues that are alive at seed maturity, but not in tissues that lose viability during seed maturation. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Phosphorylated by a tonoplast-bound calcium-dependent protein kinase. Belongs to the MIP/aquaporin (TC 1.A.8) family. TIP (TC 1.A.8.10) subfamily.