title: Structural basis for conductance by the archaeal aquaporin AqpM at 1.68 A.
abstract: To explore the structural basis of the unique selectivity spectrum and conductance of the transmembrane channel protein AqpM from the archaeon Methanothermobacter marburgensis, we determined the structure of AqpM to 1.68-A resolution by x-ray crystallography. The structure establishes AqpM as being in a unique subdivision between the two major subdivisions of aquaporins, the water-selective aquaporins, and the water-plus-glycerol-conducting aquaglyceroporins. In AqpM, isoleucine replaces a key histidine residue found in the lumen of water channels, which becomes a glycine residue in aquaglyceroporins. As a result of this and other side-chain substituents in the walls of the channel, the channel is intermediate in size and exhibits differentially tuned electrostatics when compared with the other subfamilies.
authors.affiliation: Macromolecular Structure Group, Department of Biochemistry and Biophysics, University of California, S-412C Genentech Hall, 600 16th Street, San Francisco, CA 94143-2240, USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Lee
authors.forename: David
authors.initials: D
authors.lastname: Kozono
authors.forename: Jonathan
authors.initials: J
authors.lastname: Remis
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Kitagawa
authors.forename: Peter
authors.initials: P
authors.lastname: Agre
authors.forename: Robert M
authors.initials: RM
authors.lastname: Stroud
mesh_terms: D000595:Amino Acid Sequence; D020346:Aquaporins / Q000737:chemistry* / Q000378:metabolism; D001105:Archaea / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003902:Detergents / Q000494:pharmacology; D005990:Glycerol / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D006358:Hot Temperature; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000737:chemistry; D017013:Methanobacteriaceae / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D020346:Aquaporins; D003902:Detergents; D008081:Liposomes; D011994:Recombinant Proteins; D014867:Water; D005990:Glycerol; D005998:Glycine