[摘要]：Prx4 (peroxiredoxin 4) is the only peroxiredoxin located in the ER (endoplasmic reticulum) and a proposed scavenger for H(2)O(2). In the present study, we solved crystal structures of human Prx4 in three different redox forms and characterized the reaction features of Prx4 with H(2)O(2). Prx4 exhibits a toroid-shaped decamer constructed of five catalytic dimers. Structural analysis revealed conformational changes around helix alpha 2 and the C-terminal reigon with a YF (Tyr-Phe) motif from the partner subunit, which are required for interchain disulfide formation between Cys(87) and Cys(208), a critical step of the catalysis. The structural explanation for the restricting role of the YF motif on the active site dynamics is provided in detail. Prx4 has a high reactivity with H(2)O(2), but is susceptible to overoxidation and consequent inactivation by H(2)O(2). Either deletion of the YF motif or dissociation into dimers decreased the susceptibility of Prx4 to overoxidation by increasing the flexibility of Cys(87).
