Helical image reconstruction of the outward-open human erythrocyte band 3 membrane domain in tubular crystals.
The C-terminal membrane domain of erythrocyte band 3 functions as an anion exchanger. Here, we report the three-dimensional (3D) structure of the membrane domain in an inhibitor-stabilized, outward-open conformation at 18A resolution. Unstained, frozen-hydrated tubular crystals containing the membrane domain of band 3 purified from human red blood cells (hB3MD) were examined using cryo-electron microscopy and iterative helical real-space reconstruction (IHRSR). The 3D image reconstruction of the tubular crystals showed the molecular packing of hB3MD dimers with dimensions of 60 x 110 A in the membrane plane and a thickness of 70A across the membrane. Immunoelectron microscopy and carboxyl-terminal digestion demonstrated that the intracellular surface of hB3MD was exposed on the outer surface of the tubular crystal. A 3D density map revealed that hB3MD consists of at least two subdomains and that the outward-open form is characterized by a large hollow area on the extracellular surface and continuous density on the intracellular surface.
Yamaguchi
Tomohiro
T
RIKEN SPring-8 Center, Harima Institute, Hyogo, Japan.
Fujii
Takashi
T
Abe
Yoshito
Y
Hirai
Teruhisa
T
Kang
Dongchon
D
Namba
Keiichi
K
Hamasaki
Naotaka
N
Mitsuoka
Kaoru
K
D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism; D006801:Humans; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron; D017434:Protein Structure, Tertiary
D001457:Anion Exchange Protein 1, Erythrocyte