Although many aquaporins function as always-open channels, a subgroup of aquaporins, particularly in plants have evolved a sophisticated molecular mechanism through which the channel can be closed in response to harsh conditions of the environment, under which exchange of water can be harmful for the organism.. Aquaporins are also known as water channels and are considered to be ‘the plumbing system for cells’ [15,16].for decades it was assumed that water simply leaked through biological membranes by numerous processes described above. however, these methods of water permeability could not come close to explaining the rapid movement of water across some cells.. Water channel proteins, aqps (aquaporins), of the pip (plasma membrane intrinsic protein) subfamily, provide a means for fine and quick adjustments of the plant water status. a molecular model for gating of pips by cytosolic protons (h(+)) and divalent cations was derived from the atomic structure of spinach sopip2;1 (spinacia oleracea pip2;1) in an open- and a closed-pore conformation..
What are aquaporins? aquaporins (often called aquaporin water channels) are a family of small, integral membrane proteins that are expressed broadly throughout the animal and plant kingdoms. they have a similar basic structure, with aquaporin monomers consisting of six transmembrane helical segments and two short helical segments that surround cytoplasmic and extracellular vestibules connected. Population shift between the open and closed states changes the water permeability of an aquaporin z mutant. xin l(1), hélix-nielsen c, su h, torres j, tang c, wang r, fane ag, mu y. author information: (1)school of civil and environmental engineering, nanyang technological university, singapore.. The 3-d structures of the open and closed forms of plant aquaporins, pip1 and pip2, have been solved ( ). in the closed conformation, loop d caps the channel from the cytoplasm and thereby occludes the pore. in the open conformation, loop d is displaced up to 16 Å, and this movement opens a hydrophobic gate blocking the channel entrance from.
