Role of prolines in PIP2 aquaporin gating mechanism

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

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Biofísica; 2022

PIP2 aquaporins allows the passage of H2O and H2O2 through plant cell plasmamembranes. These channels have the typical fold found in all members of the MIP(membrane intrinsic protein) family: a main structural core of with 6 transmembranealpha helices, a 7th pseudo transmembrane domain and 5 connecting loops, with N andC-termini on the cytoplasmic side. PIP2 intracellular loopD is involved in a gatingmechanism triggered by cytosolic acidification. Some aspects of this gating process havebeen elucidated, however the role of conserved Pro residues that can be crucial for theopen-closed conformational change haven’t been explored yet. Pro are unique residuesdue to their unusual characteristics compared to the other canonical amino acids. So, toelucidate the role of Pro residues located in PIP2 flexible domains, we studied watertransport activity (by overexpressing PIP2 in X. laevis oocytes) and channel dynamics (bymolecular dynamic simulations) for both wild type (WT) and mutants. Our preliminaryresults show that: i-Pro24, 25 and 26 of NT are involved in pH sensing, the replacement ofthese 3 residues by Ala shifts the pH0,5 of the activity pH dependence to more alkalinevalues (6.43±0.01 for WT n=3, 6.725±0.005 n=2 for the mutant channel, p