Gating modules of the AMPA receptor pore domain revealed by unnatural amino acid mutagenesis

Glutamate receptors are membrane proteins that incorporate an ion channel domain. Binding of the neurotransmitter glutamate opens the ion channel, a key event in neurotransmission, but also triggers other dynamic changes in protein structure. We have probed these changes in the membrane domain using light-sensitive unnatural amino acids at 30 sites. This approach allowed us to use ultraviolet light to progressively perturb receptor structure local to specified sites. We identify the collar domain and the selectivity filter, a structure that determines the permeant ion species, as exerting unexpectedly broad control over the gating and desensitization of the receptor. This work supports the idea of a dynamic selectivity filter, which in turn, may facilitate pharmacological intervention at this essential receptor.