title: The 1.3-A resolution structure of Nitrosomonas europaea Rh50 and mechanistic implications for NH3 transport by Rhesus family proteins.
abstract: The Rhesus (Rh) proteins are a family of integral membrane proteins found throughout the animal kingdom that also occur in a number of lower eukaryotes. The significance of Rh proteins derives from their presence in the human red blood cell membrane, where they constitute the second most important group of antigens used in transfusion medicine after the ABO group. Rh proteins are related to the ammonium transport (Amt) protein family and there is considerable evidence that, like Amt proteins, they function as ammonia channels. We have now solved the structure of a rare bacterial homologue (from Nitrosomonas europaea) of human Rh50 proteins at a resolution of 1.3 A. The protein is a trimer, and analysis of its subunit interface strongly argues that all Rh proteins are likely to be homotrimers and that the human erythrocyte proteins RhAG and RhCE/D are unlikely to form heterooligomers as previously proposed. When compared with structures of bacterial Amt proteins, NeRh50 shows several distinctive features of the substrate conduction pathway that support the concept that Rh proteins have much lower ammonium affinities than Amt proteins and might potentially function bidirectionally.
authors.affiliation: Biomolecular Research, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
authors.forename: Domenico
authors.initials: D
authors.lastname: Lupo
authors.forename: Xiao-Dan
authors.initials: XD
authors.lastname: Li
authors.forename: Anne
authors.initials: A
authors.lastname: Durand
authors.forename: Takashi
authors.initials: T
authors.lastname: Tomizaki
authors.forename: Baya
authors.initials: B
authors.lastname: Cherif-Zahar
authors.forename: Giorgio
authors.initials: G
authors.lastname: Matassi
authors.forename: Mike
authors.initials: M
authors.lastname: Merrick
authors.forename: Fritz K
authors.initials: FK
authors.lastname: Winkler
mesh_terms: D000595:Amino Acid Sequence; D000641:Ammonia / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D017136:Ion Transport; D026901:Membrane Transport Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D043370:Nitrosomonas europaea / Q000378:metabolism*; D010649:Phenylalanine / Q000737:chemistry; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D010649:Phenylalanine; D000641:Ammonia