TY - JOUR
T1 - Co-axial association of recombinant eye lens aquaporin-0 observed in loosely packed 3D crystals
AU - Palanivelu, Dinesh V.
AU - Kozono, David E.
AU - Engel, Andreas
AU - Suda, Kitaru
AU - Lustig, Ariel
AU - Agre, Peter
AU - Schirmer, Tilman
N1 - Funding Information:
This work was funded by the Swiss National Science Foundation grant 31-53727.98 to T.S. We thank Zora Markovic-Housley and Carmen Chan for critical reading of the manuscript, and Dimitrios Fotiadis, Herve Remigy and George Orriss for advice and support. Special thanks to Caroline Peneff-Verheyden and the staff of beamline X06SA of the SLS synchrotron (Villigen, Switzerland) for assistance with data acquisition.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2006/1/27
Y1 - 2006/1/27
N2 - Aquaporin-0 (AQP0) is the major membrane protein in vertebrate eye lenses. It has been proposed that AQP0 tetramers mediate contact between membranes of adjacent lens fiber cells, which would be consistent with the extraordinarily narrow inter-cellular spacing. We have obtained 3D crystals of recombinant bovine AQP0 that diffract to 7.0 Å resolution. The crystal packing was determined by molecular replacement and shows that, within the cubic lattice, AQP0 tetramers are associated head-to-head along their 4-fold axes. Oligomeric states larger than the tetramer were also observed in solution by native gel electrophoresis and analytical ultracentrifugation methods. In the crystals, there are no direct contacts between octamers, and it can thus be inferred that crystalline order is mediated solely by the detergent belts surrounding the membrane protein. Across the tetramer-tetramer interface, extracellular loops A and C interdigitate at the center and the perimeter of the octamer, respectively. The octamer structure is compared with that of the recently determined structure of truncated ovine AQP0 derived from electron diffraction of 2D crystals. Intriguingly, also in these crystals, octamers are observed, but with significantly different relative tetramer-tetramer orientations. The interactions observed in the loosely packed 3D crystals reported here may in fact represent an in vivo association mode between AQP0 tetramers from juxtaposed membranes in the eye lens.
AB - Aquaporin-0 (AQP0) is the major membrane protein in vertebrate eye lenses. It has been proposed that AQP0 tetramers mediate contact between membranes of adjacent lens fiber cells, which would be consistent with the extraordinarily narrow inter-cellular spacing. We have obtained 3D crystals of recombinant bovine AQP0 that diffract to 7.0 Å resolution. The crystal packing was determined by molecular replacement and shows that, within the cubic lattice, AQP0 tetramers are associated head-to-head along their 4-fold axes. Oligomeric states larger than the tetramer were also observed in solution by native gel electrophoresis and analytical ultracentrifugation methods. In the crystals, there are no direct contacts between octamers, and it can thus be inferred that crystalline order is mediated solely by the detergent belts surrounding the membrane protein. Across the tetramer-tetramer interface, extracellular loops A and C interdigitate at the center and the perimeter of the octamer, respectively. The octamer structure is compared with that of the recently determined structure of truncated ovine AQP0 derived from electron diffraction of 2D crystals. Intriguingly, also in these crystals, octamers are observed, but with significantly different relative tetramer-tetramer orientations. The interactions observed in the loosely packed 3D crystals reported here may in fact represent an in vivo association mode between AQP0 tetramers from juxtaposed membranes in the eye lens.
KW - Eye lens
KW - MIP26
KW - Membrane protein
KW - Mixed micelle
KW - X-ray crystallography
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U2 - 10.1016/j.jmb.2005.10.032
DO - 10.1016/j.jmb.2005.10.032
M3 - Article
C2 - 16309700
AN - SCOPUS:29144496893
SN - 0022-2836
VL - 355
SP - 605
EP - 611
JO - Journal of molecular biology
JF - Journal of molecular biology
IS - 4
ER -