title: A conserved cysteine residue is involved in disulfide bond formation between plant plasma membrane aquaporin monomers.
abstract: AQPs (aquaporins) are conserved in all kingdoms of life and facilitate the rapid diffusion of water and/or other small solutes across cell membranes. Among the different plant AQPs, PIPs (plasma membrane intrinsic proteins), which fall into two phylogenetic groups, PIP1 and PIP2, play key roles in plant water transport processes. PIPs form tetramers in which each monomer acts as a functional channel. The intermolecular interactions that stabilize PIP oligomer complexes and are responsible for the resistance of PIP dimers to denaturating conditions are not well characterized. In the present study, we identified a highly conserved cysteine residue in loop A of PIP1 and PIP2 proteins and demonstrated by mutagenesis that it is involved in the formation of a disulfide bond between two monomers. Although this cysteine seems not to be involved in regulation of trafficking to the plasma membrane, activity, substrate selectivity or oxidative gating of ZmPIP1s (Zm is Zea mays), ZmPIP2s and hetero-oligomers, it increases oligomer stability under denaturating conditions. In addition, when PIP1 and PIP2 are co-expressed, the loop A cysteine of ZmPIP1;2, but not that of ZmPIP2;5, is involved in the mercury sensitivity of the channels.
authors.affiliation: Institut des Sciences de Vie, Université Catholique de Louvain, Croix du Sud, 4-L7.07.14, 1348 Louvain-la-Neuve, Belgium.
authors.forename: Gerd P
authors.initials: GP
authors.lastname: Bienert
authors.forename: Damien
authors.initials: D
authors.lastname: Cavez
authors.forename: Arnaud
authors.initials: A
authors.lastname: Besserer
authors.forename: Marie C
authors.initials: MC
authors.lastname: Berny
authors.forename: Dimitri
authors.initials: D
authors.lastname: Gilis
authors.forename: Marianne
authors.initials: M
authors.lastname: Rooman
authors.forename: François
authors.initials: F
authors.lastname: Chaumont
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism*; D005260:Female; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000378:metabolism; D014982:Xenopus laevis; D003313:Zea mays / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D004220:Disulfides; D010940:Plant Proteins; D012333:RNA, Messenger; C110065:major intrinsic protein, plant; D014867:Water; D003545:Cysteine