title: Three-dimensional map of the dimeric membrane domain of the human erythrocyte anion exchanger, Band 3.
abstract: The electroneutral exchange of chloride and bicarbonate across the human erythrocyte membrane is facilitated by Band 3, a 911 amino acid glycoprotein consisting of a 43 kDa N-terminal cytosolic domain that binds the cytoskeleton, haemoglobin and glycolytic enzymes and a 52 kDa C-terminal membrane domain that mediates anion transport. Electron microscopy and three-dimensional image reconstruction of negatively stained two-dimensional crystals of the dimeric membrane domain revealed a U-shaped structure with dimensions of 60 x 110 A, and a thickness of 80 A. The structure is open on the top and at the sides, with the monomers in close contact at the base. The basal domain is 40 A thick and probably spans the lipid bilayer. The upper part of the dimer consists of two elongated protrusions measuring 25 x 80 A in projection, with a thickness of 40 A. The protrusions form the sides of a canyon, enclosing a wide space that narrows down and converges into a depression at the centre of the dimer on the top of the basal domain. This depression may represent the opening to a transport channel located at the dimer interface. Based on the available protein-chemical data, the two protrusions face the cytosolic side of the membrane and they appear to be dynamic.
authors.affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.
authors.forename: D N
authors.initials: DN
authors.lastname: Wang
authors.forename: V E
authors.initials: VE
authors.lastname: Sarabia
authors.forename: R A
authors.initials: RA
authors.lastname: Reithmeier
authors.forename: W
authors.initials: W
authors.lastname: Kühlbrandt
mesh_terms: D000595:Amino Acid Sequence; D001457:Anion Exchange Protein 1, Erythrocyte / Q000648:ultrastructure*; D000838:Anions / Q000378:metabolism; D001692:Biological Transport; D003461:Crystallography; D004912:Erythrocytes / Q000648:ultrastructure*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008961:Models, Structural; D008969:Molecular Sequence Data; D016624:Negative Staining; D011487:Protein Conformation
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D000838:Anions