Structural basis of the permeation function of plant aquaporins

Abstract

Aquaporins facilitate rapid and selective bidirectional water and uncharged low-molecular-mass solute or ion movements in response to osmotic gradients. The term ‘aquaporin’ was coined by Peter Agre and colleagues, who in 1993 suggested that major intrinsic proteins (MIPs) that facilitate rapid and selective movement of water in the direction of an osmotic gradient be named ‘aquaporins (AQPs)’ (Agre et al. 1993). Aquaporins are spread across all kingdoms of life including archaea, bacteria, protozoa, yeasts, plants and mammals. Plant aquaporins are classified within the ancient superfamily of MIPs, and based on sequence homology and subcellular localisation, they constitute several subfamilies. Genome-wide identifications of aquaporin genes are now available from around 15 plant species, and this information provides a rich source of sequence data for molecular studies through structural bioinformatics, three-dimensional (3D) modelling and molecular dynamics simulations. These studies have capacity to reveal new information, unavailable to X-ray diffraction studies of time- and space-averaged molecules confined in crystal lattices.