6NZK:
reference: Structural basis for human coronavirus attachment to sialic acid receptors., Alejandra Tortorici M, Walls AC, Lang Y, Wang C, Li Z, Koerhuis D, Boons GJ, Bosch BJ, Rey FA, de Groot RJ, Veesler D, Nat Struct Mol Biol. 2019 Jun;26(6):481-489. doi: 10.1038/s41594-019-0233-y. Epub, 2019 Jun 3. PMID: 31160783

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