Open AccessInteraction of ω‐conotoxin and the membrane calcium transport system of Escherichia coli
Author(s) -
Tisa Louis S
Publication year - 2000
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2000.tb09175.x
Subject(s) - mutant , vesicle , chemistry , biophysics , binding site , calcium , escherichia coli , biochemistry , membrane , biology , gene , organic chemistry
ω‐Conotoxin, a calcium channel blocker, inhibits chemotaxis by Escherichia coli . To test whether ω‐conotoxin acts at the cytoplasmic membrane, the kinetics of 125 I‐ω‐conotoxin binding was investigated. 125 I‐ω‐Conotoxin bound to Tris–EDTA‐permeabilized cells or right‐side‐out membrane vesicles with saturation kinetics. Binding of 125 I‐ω‐conotoxin to membrane vesicles was inhibited by Ca 2+ ions, but not by Mg 2+ ions. The calA mutant, defective in calcium transport, was more resistant to ω‐conotoxin inhibition of chemotaxis than the parental wild‐type. 125 I‐ω‐Conotoxin binding to membrane vesicles indicated that both the wild‐type and the calA mutant had similar K D s for ω‐conotoxin binding. However, the saturation level was higher with the calA mutant, indicating that there are more binding sites in the calA mutant. Thus, calA does not directly affect the affinity of the ω‐conotoxin binding site. Chemical cross‐linking experiments identified two proteins as potential ω‐conotoxin receptors.