3AM6:
reference: Crystal structure of the eukaryotic light-driven proton-pumping rhodopsin, Acetabularia rhodopsin II, from marine alga., Wada T, Shimono K, Kikukawa T, Hato M, Shinya N, Kim SY, Kimura-Someya T, Shirouzu M, Tamogami J, Miyauchi S, Jung KH, Kamo N, Yokoyama S, J Mol Biol. 2011 Sep 2;411(5):986-98. Epub 2011 Jun 25. PMID: 21726566

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