1N9Y:
reference: Structural studies of hydrogen bonds in the high-affinity streptavidin-biotin complex: mutations of amino acids interacting with the ureido oxygen of biotin., Le Trong I, Freitag S, Klumb LA, Chu V, Stayton PS, Stenkamp RE, Acta Crystallogr D Biol Crystallogr 2003 Sep;59(Pt 9):1567-73. PMID: 12925786

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