5GNB:
reference: Crystal structure of the receptor binding domain of the spike glycoprotein of human betacoronavirus HKU1., Ou X, Guan H, Qin B, Mu Z, Wojdyla JA, Wang M, Dominguez SR, Qian Z, Cui S, Nat Commun. 2017 May 23;8:15216. doi: 10.1038/ncomms15216. PMID: 28534504

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