title: In vitro analysis and modification of aquaporin pore selectivity.
abstract: Aquaporins enable the passage of a diverse set of solutes besides water. Many novel aquaporin permeants, such as antimonite and arsenite, silicon, ammonia, and hydrogen peroxide, have been described very recently. By the same token, the number of available aquaporin sequences has rapidly increased. Yet, sequence analyses and structure models cannot reliably predict permeability properties. Even the contribution to pore selectivity of individual residues in the channel layout is not fully understood. Here, we describe and discuss established in vitro assays for water and solute permeability. Measurements of volume change due to flux along osmotic or chemical gradients yield quantitative biophysical data, whereas phenotypic growth assays can hint at the relevance of aquaporins in the physiological setting of a certain cell. We also summarize data on the modification of pore selectivity of the prototypical water-specific mammalian aquaporin-1. We show that replacing residues in the pore constriction region allows ammonia, urea, glycerol, and even protons to pass the aquaporin pore.
authors.affiliation: Pharmaceutical Chemistry, University of Kiel, Gutenbergstrasse 76, Kiel, 24118, Germany. ebeitz@pharmazie.uni-kiel.de
authors.forename: Eric
authors.initials: E
authors.lastname: Beitz
authors.forename: Dana
authors.initials: D
authors.lastname: Becker
authors.forename: Julia
authors.initials: J
authors.lastname: von Bülow
authors.forename: Christina
authors.initials: C
authors.lastname: Conrad
authors.forename: Nadine
authors.initials: N
authors.lastname: Fricke
authors.forename: Amornrat
authors.initials: A
authors.lastname: Geadkaew
authors.forename: Dawid
authors.initials: D
authors.lastname: Krenc
authors.forename: Jie
authors.initials: J
authors.lastname: Song
authors.forename: Dorothea
authors.initials: D
authors.lastname: Wree
authors.forename: Binghua
authors.initials: B
authors.lastname: Wu
mesh_terms: D000641:Ammonia / Q000378:metabolism; D000818:Animals; D051398:Aquaporin 1 / Q000378:metabolism; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001681:Biological Assay / Q000379:methods; D002478:Cells, Cultured; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D007891:Leishmania / Q000254:growth & development / Q000378:metabolism; D008958:Models, Molecular; D009865:Oocytes / Q000378:metabolism; D010539:Permeability; D017354:Point Mutation; D011487:Protein Conformation; D011522:Protons; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014508:Urea / Q000378:metabolism; D014867:Water / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism; D015003:Yeasts / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D020346:Aquaporins; D011522:Protons; D011994:Recombinant Proteins; D014867:Water; D051398:Aquaporin 1; D000641:Ammonia; D014508:Urea; D005990:Glycerol