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. 2011 Oct 28;6(10):e26367. doi: 10.1371/journal.pone.0026367

Figure 2. Thrombin catalytic triads in s-variegin-bound and hirugen-bound structures.

Figure 2

(A) Thrombin catalytic triad THis57, TAsp102 and TSer195 in thrombin:hirugen structure (green) and in thrombin:s-variegin structure (pink) are superimposed. The TSer195 Oγ in thrombin:s-variegin structure is displaced by 1.19 Å compared to thrombin:hirugen structure. The displacement of TSer195 Oγ in thrombin:s-variegin structure (pink) is due to interactions with VHis12 of s-variegin through hydrogen bond (dotted arrow), rendering TSer195 a weak nucleophile that is incapable of catalysis. The imidazole ring of THis57 also rotated, resulted in a displacement of its Nε by 0.56 Å. Overall, the distance between Nε of THis57 and Oγ of TSer195 increases to 3.60 Å (black arrow) from 2.79 Å (green arrow), disrupts the catalytic charge relay system. (B) The 2Fo-Fc electron density map of thrombin catalytic triad and VHis12 contoured at 1.0σ.