Structure of BC3987 active site.

(A) The active site and immediate surroundings in BC3987. Thr8 and Thr53 can possibly form hydrogen bonds to the Sγ-atom of Cys15 upon reduction of the disulfide bridge. The |2Fo–Fc| map is contoured at 1.5 σ. (B) The wild type (in brown) and T8A (in blue) crystal structures have CPPC active sites that superimpose with a RMS value of 0.053 Å. This verifies that the mutation does not disturb the CPPC active site. (C) Comparison of C-P-P-C motifs in oxidized BC3987 (in brown), reduced Tryparedoxin, TXN-II, (in green), and reduced Trx h1 (in grey). From this superimposition, it is suggested that the cysteine side chains and not the backbone undergo the largest structural rearrangement upon reduction of the active site.