Mechanistic insight into pH gating in PIP aquaporins: role of specific loopD amino acids

AGUSTINA CANESSA FORTUNA; GERARDO ZERBETTO DE PALMA; VICTORIA VITALI; ARI ZEIDA; DARIO ESTRIN; KARINA ALLEVA

Congreso; 20 th IUPAB Congress, 45 th Annual SBBf Meeting, and 50 th Annual SBBq Meeting; 2021

Aquaporins are membrane channels that transport water and other solutes. Their transport activity is regulated by different stimuli such as pH, ions, phosphorylation/dephosphorylation and interaction with other proteins. All aquaporins share tetrameric quaternary structures with two conserved regions that regulate the specificity of transport: the Asn-Pro-Ala (NPA) motives and the aromatic/arginine (Ar/R) selectivity filter. In particular, plantPIP aquaporins present a longer loopD which is involved in its gating mechanism. The open/closed conformational transition is triggered by intracellular acidification and different pH0,5 are found for PIP2 homotetramers and for PIP2-PIP1 heterotertamers. Our goal is to elucidate the role of specific LoopD? s aminoacids in the modulation of PIP gating mechanism by intracellular pH. Ourin vitro and in silico experiments, for wild type and mutant PIP show that: i- a conserved Leu residue in the cytoplasmic constriction is the structural element that determines pore blockage and, ii- a Pro residue present in PIP2 but not in PIP1 channels is involved in differential pH0.5 of homo and heterotetramers dose-response curves. So, two loopD residues, Leu 206 and Pro 194, works in combination with the pH sensor His 202 to control effective pore closing