4FXK:
reference: Structural basis for activation of the complement system by component C4 cleavage., Kidmose RT, Laursen NS, Dobo J, Kjaer TR, Sirotkina S, Yatime L, Sottrup-Jensen L, Thiel S, Gal P, Andersen GR, Proc Natl Acad Sci U S A. 2012 Sep 4. PMID: 22949645

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