1ST3:
reference: The crystal structure of the Bacillus lentus alkaline protease, subtilisin BL, at 1.4 A resolution., Goddette DW, Paech C, Yang SS, Mielenz JR, Bystroff C, Wilke ME, Fletterick RJ, J Mol Biol 1992 Nov 20;228(2):580-95. PMID: 1453465

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