FIG. 7.

Quaternary structures of Prxs. For some Prxs, the basic monomeric structure shown in Fig. 2 can form (A) A-type dimers, interacting near α3, or (B) B-type dimers, interacting at the β-sheet to form an extended 10-stranded β-sheet. (C) Some members of the Prx1 and Prx6 subfamilies form decameric structures through the interaction of five B-type dimers via the A-type dimer interface. Subunit coloring for the A-type dimer (purple and dark blue) and the B-type dimer (dark blue and light blue) are used in the decamer to show how it is composed of these two types of interactions. (D) The oligomerization of the decamers is redox dependent. In the Prx1 and Prx6 subfamilies, reduced and overoxidized Prxs form decamers, with the A-type dimer interface stabilizing the FF active site. The structural change with disulfide formation destabilizes the A-type dimer interface, and the decamer falls apart to B-type dimers. Octamers and dodecamers have also been observed (see Table 1) and are thought to be functionally equivalent to the decamer. (A–C) were prepared by using Pymol (20). (To see this illustration in color the reader is referred to the web version of this article at www.liebertonline.com/ars).