A possible biological role of the electron transfer between tyrosine and tryptophan

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Abstract
Experiments have demonstrated that four tryptophan residues are located near the tetrodotoxin binding site in Na+ channels, and that conserved tyrosine and tryptophan residues are located in the pore‐forming region of voltage‐sensitive K+ channels. This paper proposes an activation mechanism involving electron transfer between these residues. The K+ channel may be closed by four tyrosine residues forming hydrogen bonds with each other. After electron transfer, these hydrogen bonds will be broken, thereby opening the channel. The Na+ channel could be activated by a similar mechanism. This idea can be tested directly by observing tyrosine or tryptophan radicals when the channels are in the open state.