4QRY:
reference: Crystal Structures of the L1, L2, N, and O States of pharaonis Halorhodopsin., Kouyama T, Kawaguchi H, Nakanishi T, Kubo H, Murakami M, Biophys J. 2015 Jun 2;108(11):2680-90. doi: 10.1016/j.bpj.2015.04.027. PMID: 26039169

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