Open AccessTwo-dimensional crystals of cholera toxin B-subunit-receptor complexes: projected structure at 17-A resolution.
Author(s) -
David S. Ludwig,
Hans O. Ribi,
Gary K. Schoolnik,
Roger D. Kornberg
Publication year - 1986
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.83.22.8585
Subject(s) - pentamer , crystallography , protein subunit , cholera toxin , resolution (logic) , negative stain , ganglioside , crystal structure , hexagonal lattice , chemistry , electron micrographs , lattice (music) , electron microscope , biophysics , materials science , biology , optics , physics , biochemistry , condensed matter physics , artificial intelligence , antiferromagnetism , computer science , acoustics , microbiology and biotechnology , gene
The B subunit of cholera toxin forms two-dimensional crystals when bound to its membrane receptor, ganglioside GM1, in phospholipid layers. A rectangular crystal lattice gives diffraction extending to 15-A resolution in negative stain, and image-processing of electron micrographs reveals a ring of five protein densities. The diameter of the central hole and the outer diameter of the ring are about 20 and 60 A, respectively. These data are consistent with a pentameric, doughnut-shaped structure of the B subunit that lies flat on a membrane surface. A hexagonal crystal lattice is obtained as well, and results of image processing and chemical crosslinking allow two interpretations: the B subunit may exist in both pentameric and hexameric forms or, more likely, the hexagonal lattice may represent a disordered or liquid crystalline form, in which a pentamer undergoes rotational averaging about its 5-fold axis.