(full paper is archived in the Miller Library)
Title: pH-dependance and mechanism of tityustoxin block of SqKv1A K+ channels
Student Author(s): Pugh, Jason
Faculty Advisor(s): Gilly, William
Location: Final Papers Biology 175H
Date: June 1999
Abstract: Tityustoxin block of wild type and mutant SqKV1A channels from Loligo opalesceus neurons was studied in Xenopus oocytes using the two electrode voltage clamp method. The mutant channel was created by replacing a histidine residue at position 351 on the outer vestibule with a glycine. Wild type channels show greatly reduced sensitivity to tityustoxin block at pH 6. The glycine mutant's sensitivity to tydioustoxin was not pH dependent. Block of both the wild type and mutant channels proved to be voltage dependent. Kd values ranged from 14 nm at 0 mv to 70 nm at 100 mv for both channels. K-on rates of H351 channels were not effected by voltage, whereas K-on rates of wild-type channels decreased slightly with voltage. K-off rates increased as voltage increased in both types of channels. Results suggests that a charged residue on the toxin enters the channel pore when tityustoxin blocks these channels, making the toxin sensitive to the membrane voltage.