Gating in plant plasma membrane aquaporins: the involvement of leucine in the formation of a pore constriction in the closed state

ZERBETTO DE PALMA, GERARDO; VITALI, VICTORIA; ALLEVA, KARINA; ALIPERTI CAR, LUCIO; ZEIDA, ARI; ALIPERTI CAR, LUCIO; ZEIDA, ARI; CANESSA FORTUNA, AGUSTINA; ARMENTIA, LUCIANO; ESTRIN, DARÍO A.; CANESSA FORTUNA, AGUSTINA; ARMENTIA, LUCIANO; ESTRIN, DARÍO A.; ZERBETTO DE PALMA, GERARDO; VITALI, VICTORIA; ALLEVA, KARINA

FEBS JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019 vol. 286 p. 3473 - 3487

1742-464X

The control of water permeability in plant PIP2 aquaporins has become a paradigmatic case study of the capping mechanism for pore closure in water channels. From structural data, it has been postulated that the gating process in PIP2 involves a conformational rearrangement in cytosolic loopD that generates an obstruction to the transport of water molecules inside the aquaporin pore. BvPIP2;2 is a PIP2 aquaporin from Beta vulgaris whose pH response has been thoroughly characterized. In this work, we study the participation of Leu206 in BvPIP2;2 gating triggered by cytosolic acidification and show that this residue acts as a plug that blocks water transport. Based on data obtained from in silico and in vitro studies, we demonstrate that Leu206, one of the residues lining the pore, is respon sible for ~ 60% of water blockage. Cell osmotic swelling experiments andatomistic molecular dynamics simulations indicate that the replacement of Leu206 by an Ala residue maintains high water permeability under conditions where the pore is expected to be closed. The present work demonstrates that Leu206, located at the cytoplasmic entry of the channel,constitutes a crucial pH-sensitive steric gate regulating water transport in PIP aquaporins.