3I1K:
reference: Structural basis for ligand and substrate recognition by torovirus hemagglutinin esterases., Langereis MA, Zeng Q, Gerwig GJ, Frey B, von Itzstein M, Kamerling JP, de Groot RJ, Huizinga EG, Proc Natl Acad Sci U S A. 2009 Aug 31. PMID: 19721004

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