In vitro analysis and modification of aquaporin pore selectivity.
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.
Beitz
Eric
E
Pharmaceutical Chemistry, University of Kiel, Gutenbergstrasse 76, Kiel, 24118, Germany. ebeitz@pharmazie.uni-kiel.de
Becker
Dana
D
von Bülow
Julia
J
Conrad
Christina
C
Fricke
Nadine
N
Geadkaew
Amornrat
A
Krenc
Dawid
D
Song
Jie
J
Wree
Dorothea
D
Wu
Binghua
B
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
D020346:Aquaporins; D011522:Protons; D011994:Recombinant Proteins; D014867:Water; D051398:Aquaporin 1; D000641:Ammonia; D014508:Urea; D005990:Glycerol