The crystal structure of α-bungarotoxin at 2.5 Å resolution: relation to solution structure and binding to acetylcholine receptor

Publisher Website
Google Scholar
Abstract
We report collection of 2.5 Å resolution X-ray diffraction data from newly grown crystals of the rare ‘small unit cell’ form of the long snake neurotoxin, α-bungarotoxin. The previous model of the molecule has been rebuilt, and refined using least-square methods to a crystallographic residual of 0.24 at 2.5 Å resolution. α-Bungarotoxin's crystal structure is compared with the crystal structures of two other snake neurotoxins (cobratoxin and erabutoxin), and with its solution structure inferred from spectroscopic studies. Significant differences include less β-sheet in bungarotoxm's crystal structure than in solution, or in the crystal structures of other neurotoxins, and an unusual orientation in the crystal of the invariant tryptophan. The functional, binding surface of bungarotoxin is described; it consists primarily of hydrophobic and hydrogen-bonding groups and only a few charged side chains. The structure is compared with experimental binding parameters for neurotoxins.