4ZQC:
reference: Visualizing the tunnel in tryptophan synthase with crystallography: Insights into a selective filter for accommodating indole and rejecting water., Hilario E, Caulkins BG, Huang YM, You W, Chang CE, Mueller LJ, Dunn MF, Fan L, Biochim Biophys Acta. 2016 Mar;1864(3):268-79. doi: 10.1016/j.bbapap.2015.12.006., Epub 2015 Dec 17. PMID: 26708480

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