Open AccessThe role of an invariant tryptophan residue in α‐bungarotoxin and cobrotoxin
Author(s) -
CHANG ChunChang,
KAWATA Yasushi,
SAKIYAMA Fumio,
HAYASHI Kyozo
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb19373.x
Subject(s) - tryptophan , bungarotoxin , residue (chemistry) , chemistry , antigenicity , kynurenine , toxicity , neurotoxin , toxin , biochemistry , antibody , biology , organic chemistry , amino acid , receptor , immunology , acetylcholine receptor
Ozone oxidation converted the single, invariant, tryptophan residue to N 2 ‐formylkynurenine in α‐bungarotoxin and cobrotoxin. Upon this modification, the lethal toxicity was significantly reduced in cobrotoxin but mostly retained in α‐bungarotoxin. Each neurotoxin containing kynurenine instead of tryptophan retained the same antigenicity as the native toxin. Fluorescence and CD spectroscopy revealed that, although the environment and state of the kynurenine residue were similar, [Kyn 29 ]cobrotoxin was much more sensitive to pH change than α‐[Kyn 28 ]bungarotoxin. In terms of lethal toxicity and conformational stability, the invariant tryptophan residue appears to play a more important role in cobrotoxin, imparting a higher lethal toxicity than that in α‐bungarotoxin, which has a disulfide bond at Cys29–Cys33.