IQUIFIB   02644
INSTITUTO DE QUIMICA Y FISICOQUIMICA BIOLOGICAS "PROF. ALEJANDRO C. PALADINI"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Hydrophobic gating in aquaporins: functional study of the participation of Leu206 in channel closure
Autor/es:
AGUSTINA CANESSA FORTUNA; FLORENCIA SCOCHERA; KARINA ALLEVA
Lugar:
Tucumán
Reunión:
Congreso; III LAFEBS IX IBEROAMERICAN CONGRESS OF BIOPHYSICS XLV SAB; 2016
Resumen:
PIP aquaporins are transmembrane proteins able to transport water in a strictly regulated manner. The channel closure results from either the protonation of a conserved His residue under cytosolic acidification or by dephosphorylation of conserved serine residues (1). Our group described previously that PIP can ensemble not only as homotetramers but also as heterotetramers of variable stoichiometry combining PIP2 and PIP1 isoforms; pH sensing is shifted to alkaline values favoring the persistence of the close state in all the heterotetramers formed (2).Despite functional data is abundant both for PIP2 and PIP1 isoforms, only PIP2 structure has been resolved (3). From structural data, a mechanism named ?capping? has been proposed to explain the gating of PIP aquaporins channel. This mechanism implies a large-scale rearrangement of loopD in order to cap the channel in the closed state. Interestingly, this rearrangement involves the conformation of a hydrophobic gate that completes the blocking of the water pore. While the information given by the description of this mechanism is highly detailed, up to now PIP mutants haven?t been construct to confirm computational data. The Leu206, highly conserved in PIP, is part of the hydrophobic gate and has been proposed to insert into a cavity near the entrance of the channel. We create the mutant protein BvPIP2;2Leu206Ala to evaluate the relevance of this hydrophobic residue in the blocking of the pore under acidic conditions. We study, for the first time, the impact of the hydrophobic gate both in PIP2 homotetramers and PIP2-PIP1 heterotetramers, by means of heterologous expression (Xenopus oocyte system) of the mutant alone or in combination with wild type BvPIP1;1.