1NU9:
reference: Staphylocoagulase is a prototype for the mechanism of cofactor-induced zymogen activation., Friedrich R, Panizzi P, Fuentes-Prior P, Richter K, Verhamme I, Anderson PJ, Kawabata S, Huber R, Bode W, Bock PE, Nature 2003 Oct 2;425(6957):535-9. PMID: 14523451

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