title: The arginine-facing amino acid residue of the rat aquaporin 1 constriction determines solute selectivity according to its size and lipophilicity.
abstract: Aquaporins (AQP) are transmembrane channels for small, predominantly uncharged solutes. Their selectivity is partly determined by the aromatic/arginine constriction. Ammonia is similar in size and polarity to water, yet a subset of aquaporins distinguishes between the two. We mutated the constriction of water-selective rat AQP1 to mimic that of the ammonia-permeable human AQP8 by replacing Phenylalanine 56 with histidine, Histidine 180 with isoleucine, and Cysteine 189 with glycine, alone and in combination. Only AQP1 mutants including the H180I exchange increased the ammonia and methylamine tolerance of yeast. In a second set of mutations, we replaced Histidine 180 with alanine, leucine, methionine, phenylalanine, asparagine or glutamine. AQP1 H180A was equivalent to AQP1 H180I. AQP1 H180L increased ammonia but not methylamine tolerance of yeast. AQP1 mutants with methionine, phenylalanine, asparagine or glutamine in place of Histidine 180, increased neither ammonia nor methylamine tolerance of yeast. All mutants conducted water, as judged by osmotic assays with yeast sphaeroplasts. We propose that the arginine-facing amino acid residue is the most versatile selector of aquaporin constrictions, excluding Escherichia coli glycerol facilitator-type aquaporins.
authors.affiliation: Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel , Gutenbergstrasse, Kiel , Germany.
authors.forename: Dawid
authors.initials: D
authors.lastname: Krenc
authors.forename: Jie
authors.initials: J
authors.lastname: Song
authors.forename: Abdulnasser
authors.initials: A
authors.lastname: Almasalmeh
authors.forename: Binghua
authors.initials: B
authors.lastname: Wu
authors.forename: Eric
authors.initials: E
authors.lastname: Beitz
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D051398:Aquaporin 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001120:Arginine / Q000378:metabolism*; D006801:Humans; D008744:Methylamines / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: C496022:Aqp1 protein, rat; D020346:Aquaporins; D008744:Methylamines; C108330:aquaporin 8; D051398:Aquaporin 1; D000641:Ammonia; D001120:Arginine; C027451:methylamine
keywords: Ammonia; Saccharomyces cerevisiae; aquaporin; aromatic/arginine constriction; selectivity filter