Jönsson Thomas J, Johnson Lynnette C, Lowther W Todd
Center for Structural Biology and Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA.
Nature. 2008 Jan 3;451(7174):98-101. doi: 10.1038/nature06415.
Typical 2-Cys peroxiredoxins (Prxs) have an important role in regulating hydrogen peroxide-mediated cell signalling. In this process, Prxs can become inactivated through the hyperoxidation of an active site Cys residue to Cys sulphinic acid. The unique repair of this moiety by sulphiredoxin (Srx) restores peroxidase activity and terminates the signal. The hyperoxidized form of Prx exists as a stable decameric structure with each active site buried. Therefore, it is unclear how Srx can access the sulphinic acid moiety. Here we present the 2.6 A crystal structure of the human Srx-PrxI complex. This complex reveals the complete unfolding of the carboxy terminus of Prx, and its unexpected packing onto the backside of Srx away from the Srx active site. Binding studies and activity analyses of site-directed mutants at this interface show that the interaction is required for repair to occur. Moreover, rearrangements in the Prx active site lead to a juxtaposition of the Prx Gly-Gly-Leu-Gly and Srx ATP-binding motifs, providing a structural basis for the first step of the catalytic mechanism. The results also suggest that the observed interactions may represent a common mode for other proteins to bind to Prxs.
典型的2-半胱氨酸过氧化物酶（Prxs）在调节过氧化氢介导的细胞信号传导中发挥着重要作用。在此过程中，Prxs可通过活性位点半胱氨酸残基过度氧化为半胱氨酸亚磺酸而失活。硫氧还蛋白（Srx）对该部分的独特修复可恢复过氧化物酶活性并终止信号。Prx的过度氧化形式以稳定的十聚体结构存在，每个活性位点都被掩埋。因此，尚不清楚Srx如何接近亚磺酸部分。在此，我们展示了人Srx-PrxI复合物的2.6埃晶体结构。该复合物揭示了Prx羧基末端的完全展开，以及它在远离Srx活性位点的Srx背面的意外堆积。在此界面进行的定点突变体的结合研究和活性分析表明，这种相互作用是修复发生所必需的。此外，Prx活性位点的重排导致Prx甘氨酸-甘氨酸-亮氨酸-甘氨酸和Srx ATP结合基序并列，为催化机制的第一步提供了结构基础。结果还表明，观察到的相互作用可能代表其他蛋白质与Prxs结合的一种常见模式。
