Figure 4

Plasmodium peroxiredoxin oligomeric structures. Oligomeric structures of (A) Pv Trx-Px_ox and (B) Py Trx-Px1_ox showing the internal dimer. (C) The close-up view of a hydrogen bond at the A-type interface between the side chain of Lys81 from one monomer (cyan) and the main chain carbonyl of Lys172 from an adjacent molecule (grey) with the 2mFo-dFc electron map contoured at 1.0 σ (blue mesh). (D) Examples of the novel hydrogen bonding interactions of the Py Trx-Px_ox are circled in black. The panel is simplified to show only a tetramer for clarity, but indeed there are hydrogen bonding interactions across all of the A-type interfaces. Although the hydrogen bonding interaction is at the A-type interface, it is formed between distant chains in an A-C fashion (where A, B, C, and D chains are pink, grey, cyan, and green, respectively). For example, in the pink chain Lys172 carbonyl backbone is shown hydrogen bonding with the side chain of Lys81 from the cyan chain (A-C fashion) and in the grey chain Lys81 is hydrogen bonding with the main chain carbonyl of green Lys172 (B-D fashion). A comparison of the A-type interactions (E) and B-type interactions (F) between Pv Trx-Px1 and Py Trx-Px1 is shown. In (E) and (F) the monomer structures (dark green and purple) are structurally aligned (rmsd = 0.573 Å), so that upon comparison of the corresponding dimeric partners the difference in the interfaces are shown (Pv Trx-Px1 shown in light greens and Py Trx-Px1 shown in light blue/purple). A full alignment of the A-type dimers gives a rmsd = 1.065 Å, while a full alignment of the B-type dimers gives a rmsd = 3.137 Å.