Abstract
In ion channels, “rings” of ionized side chains that decorate the walls of the permeation pathway often lower the energetic barrier to ion conduction. Using single-channel electrophysiological recordings, we studied the poorly understood ring of four glutamates (and one glutamine) that dominate this catalytic effect in the muscle nicotinic acetylcholine receptor (“the intermediate ring of charge”). We show that all four wild-type glutamate side chains are deprotonated in the 6.0–9.0 pH range; that only two of them contribute to the size of the single-channel current; that these side chains must be able to adopt alternate conformations that either allow or prevent their negative charges from increasing the rate of cation conduction; and that the location of these glutamate side chains squarely at one of the ends of the transmembrane pore is critical for their largely unshifted pKa values and for the unanticipated impact of their conformational flexibility on cation permeation.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.