Restriction of intramolecular movements within the Cry1Aa toxin molecule of Bacillus thuringiensis through disulfide bond engineering

摘要: Disulfide bridges were introduced into Cry1Aa, a Bacillus thuringiensis lepidopteran toxin, to stabilize different protein domains including domain I α-helical regions thought be involved in membrane integration and permeation. Bridged mutants could not form functional ion channels lipid bilayers the oxidized state, but upon reduction with β-mercaptoethanol, regained parental toxin channel activity. Our results show that unfolding of around hinge region linking II is necessary step for pore formation. They also suggest insertion hydrophobic hairpin made α-helices 4 5 plays critical role formation pore.