Tong Kit I, Padmanabhan Balasundaram, Kobayashi Akira, Shang Chengwei, Hirotsu Yosuke, Yokoyama Shigeyuki, Yamamoto Masayuki
Graduate School of Comprehensive Human Sciences, Center for TARA, JST-ERATO Environmental Response Project, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8577, Japan.
Mol Cell Biol. 2007 Nov;27(21):7511-21. doi: 10.1128/MCB.00753-07. Epub 2007 Sep 4.
Nrf2 is the regulator of the oxidative/electrophilic stress response. Its turnover is maintained by Keap1-mediated proteasomal degradation via a two-site substrate recognition mechanism in which two Nrf2-Keap1 binding sites form a hinge and latch. The E3 ligase adaptor Keap1 recognizes Nrf2 through its conserved ETGE and DLG motifs. In this study, we examined how the ETGE and DLG motifs bind to Keap1 in a very similar fashion but with different binding affinities by comparing the crystal complex of a Keap1-DC domain-DLG peptide with that of a Keap1-DC domain-ETGE peptide. We found that these two motifs interact with the same basic surface of either Keap1-DC domain of the Keap1 homodimer. The DLG motif works to correctly position the lysines within the Nrf2 Neh2 domain for efficient ubiquitination. Together with the results from calorimetric and functional studies, we conclude that different electrostatic potentials primarily define the ETGE and DLG motifs as a hinge and latch that senses the oxidative/electrophilic stress.
Nrf2是氧化/亲电应激反应的调节因子。其周转通过Keap1介导的蛋白酶体降解来维持,该降解通过双位点底物识别机制进行,其中两个Nrf2-Keap1结合位点形成一个铰链和锁扣。E3连接酶衔接蛋白Keap1通过其保守的ETGE和DLG基序识别Nrf2。在本研究中,我们通过比较Keap1-DC结构域-DLG肽与Keap1-DC结构域-ETGE肽的晶体复合物,研究了ETGE和DLG基序如何以非常相似的方式但具有不同的结合亲和力与Keap1结合。我们发现这两个基序与Keap1同二聚体的任一Keap1-DC结构域的相同碱性表面相互作用。DLG基序的作用是将Nrf2 Neh2结构域内的赖氨酸正确定位,以实现高效泛素化。结合量热法和功能研究的结果,我们得出结论,不同的静电势主要将ETGE和DLG基序定义为感知氧化/亲电应激的铰链和锁扣。