Argiotoxin in the closed AMPA receptor channel: experimental and modeling study.

Binding of argiotoxin in the closed state of Ca(2+)-permeable AMPA receptor channels was studied using electrophysiological and molecular modeling approaches. Experimental study unambiguously revealed that argiotoxin is trapped in the closed AMPA receptor channels after agonist dissociation. Docking of the argiotoxin to the channel model based on recently published X-ray structure demonstrated that the drug can be effectively accommodated in the cavity of the closed channel only if the terminal moiety of the molecule penetrates in the narrow portion of the pore below the selectivity filter. Combining these results, we conclude that the selectivity filter of the AMPA receptor channels is not sterically occluded in the closed state.