Prediction of arsenic and antimony transporter major intrinsic proteins from the genomes of crop plants.

Major intrinsic proteins (MIPs), commonly known as aquaporins, transport water and non-polar small solutes. Comparing the 3D models and the primary selectivity-related motifs (two Asn-Pro-Ala (NPA) regions, the aromatic/arginine (ar/R) selectivity filter, and Froger's positions (FPs)) of all plant MIPs that have been experimentally proven to transport arsenic (As) and antimony (Sb), some substrate-specific signature sequences (SSSS) or specificity determining sites (SDPs) have been predicted. These SSSS or SDPs were determined in 543 MIPs found in the genomes of 12 crop plants; the As and Sb transporters were predicted to be distributed in noduline-26 like intrinsic proteins (NIPs), and every plant had one or several As and Sb transporter NIPs. Phylogenetic grouping of the NIP subfamily based on the ar/R selectivity filter and FPs were linked to As and Sb transport. We further determined the group-wise substrate selectivity profiles of the NIPs in the 12 crop plants. In addition to two NPA regions, the ar/R filter, and FPs, certain amino acids especially in the pore line, loop D, and termini contribute to the functional distinctiveness of the NIP groups. Expression analysis of transcripts in different organs indicated that most of the As and Sb transporter NIPs were expressed in roots.