Psedo Transmembrane

1. Most aquaporins have a similar structural arrangement, consisting of a similar fold. This fold contains helices encasing a small water-conducting channel where water is able to arrange in a singular line. There are cytoplasmic and extracellular loops immersing into the membrane through opposing sides, and form two smaller helices creating a psedo transmembrane segment. Within the membrane, there are four aquaporin molecules forming a homo-tetramer, creating a fifth channel; the channel is mainly hydrophobic. However, they are some structural differences, as well as differing regulation modes. The direction of H2O molecular flow through the channel is determined by the osmotic pressure. The mechanism that prevents proton channeling is believed to be the proton exclusion mechanism and is caused by the NPA region. The macro dipoles of both of the half-helices made from the B and E loops focus an electrostatic potential that is positive, which appears to be crucial for the exclusion of protons. The water chain is in a bi-directional manner and at every half point the hydrogens located away from the center prevent the formation of dipole moments, causing a disruption within the proton wire. …show more content…
Aquaporin water transport function contains the ability to become regulated by responding to cellular or environmental signals. This is done by controlling the water transport occurring at an individual protein level through conformational changes, such as gating. The following one involves regulating at the transcriptional/translational level in addition to trafficking, in which protein molecules are rotated throughout intracellular storage vesicles, as well as target membranes. Aquaporins allow for quick and specific regulation, in which they either utilize the mechanism of gating or trafficking, depending on the signals