4U15:
reference: Modified T4 Lysozyme Fusion Proteins Facilitate G Protein-Coupled Receptor Crystallogenesis., Thorsen TS, Matt R, Weis WI, Kobilka BK, Structure. 2014 Oct 23;22(11):1657-1664. doi: 10.1016/j.str.2014.08.022. PMID: 25450769

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