5DSG:
reference: Crystal structures of the M1 and M4 muscarinic acetylcholine receptors., Thal DM, Sun B, Feng D, Nawaratne V, Leach K, Felder CC, Bures MG, Evans DA, Weis WI, Bachhawat P, Kobilka TS, Sexton PM, Kobilka BK, Christopoulos A, Nature. 2016 Mar 17;531(7594):335-40. doi: 10.1038/nature17188. Epub 2016 Mar 9. PMID: 26958838

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