4M7G:
reference: Conformational flexibility in the catalytic triad revealed by the high-resolution crystal structure of Streptomyces erythraeus trypsin in an unliganded state., Blankenship E, Vukoti K, Miyagi M, Lodowski DT, Acta Crystallogr D Biol Crystallogr. 2014 Mar;70(Pt 3):833-40. doi:, 10.1107/S1399004713033658. Epub 2014 Feb 22. PMID: 24598752

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