1Q4Z:
reference: Molecular modelling of S1 and S2 subunits of SARS coronavirus spike glycoprotein., Spiga O, Bernini A, Ciutti A, Chiellini S, Menciassi N, Finetti F, Causarono V, Anselmi F, Prischi F, Niccolai N, Biochem Biophys Res Commun 2003 Oct 10;310(1):78-83. PMID: 14511651

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