Institute of Molecular Enzymology, School of Biology & Basic Medical Sciences, Suzhou Medical College of Soochow University, Suzhou 215123, China.
MOE Key Laboratory for Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Acta Biochim Biophys Sin (Shanghai). 2022 Aug 25;54(8):1159-1170. doi: 10.3724/abbs.2022089.
The mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved in eukaryotes, regulating various cellular processes. The MAPK kinases (MKKs) are dual specificity kinases, serving as convergence and divergence points of the tripartite MAPK cascades. Here, we investigate the biochemical characteristics and three-dimensional structure of MKK5 in (AtMKK5). The recombinant full-length AtMKK5 is phosphorylated and can activate its physiological substrate AtMPK6. There is a conserved kinase interacting motif (KIM) at the N-terminus of AtMKK5, indispensable for specific recognition of AtMPK6. The kinase domain of AtMKK5 adopts active conformation, of which the extended activation segment is stabilized by the phosphorylated Ser221 and Thr215 residues. In line with sequence divergence from other MKKs, the αD and αK helices are missing in AtMKK5, suggesting that the AtMKK5 may adopt distinct modes of upstream kinase/substrate binding. Our data shed lights on the molecular mechanisms of MKK activation and substrate recognition, which may help design specific inhibitors targeting human and plant MKKs.
丝裂原活化蛋白激酶（MAPK）信号通路在真核生物中高度保守，调节各种细胞过程。MAPK 激酶（MKK）是双特异性激酶，作为三分MAPK 级联的汇聚和发散点。在这里，我们研究了 （AtMKK5）中 MKK5 的生化特性和三维结构。重组全长 AtMKK5 被磷酸化并可以激活其生理底物 AtMPK6。AtMKK5 的 N 端有一个保守的激酶相互作用基序（KIM），对于 AtMPK6 的特异性识别是必不可少的。AtMKK5 的激酶结构域采用活性构象，其中延伸的激活片段由磷酸化的 Ser221 和 Thr215 残基稳定。与其他 MKK 从序列上的差异一致，AtMKK5 缺失了 αD 和 αK 螺旋，这表明 AtMKK5 可能采用不同的上游激酶/底物结合方式。我们的数据揭示了 MKK 激活和底物识别的分子机制，这可能有助于设计针对人和植物 MKK 的特异性抑制剂。
