SPECIFICITY AND DIMERIZATION IN MAP KINASE INTERACTIONS

MAP激酶是一个多效蛋白激酶大家族，其转导信号导致多种调节事件，包括增殖、分化功能和对环境损害的反应。MAP激酶ERK1和ERK2响应导致生长和分化的信号。相关的MAP激酶p38和其他同源物参与应激反应。MAP激酶家族成员都与底物和上游激活因子有独特的相互作用，以确保忠实的信号传导。我们之前确定了ERK2和p38的低活性形式，以及ERK2的活性形式的结构。我们将继续对该家族进行结构研究，并分析MAP激酶与多肽和全长蛋白的相互作用，以确定MAP激酶ERK2和p38与转录因子和蛋白激酶底物选择性相互作用的结构基础。我们发现ERK2在磷酸化时二聚体，活性ERK2的结构显示为二聚体。许多MAP激酶底物是二聚体。二聚化现象在信号传导过程中普遍存在，并可能通过提高对正确底物的选择性来对信号的正确靶向做出重大贡献。在这项研究中，我们将对活性二聚体ERK2和活性二聚化缺陷突变体进行动力学分析，以确定二聚化对转录因子底物活性的影响。

MAP kinases are a large family of pleiotropic protein kinases that transduce signals leading to diverse regulatory events, including proliferation, differentiated functions, and responses to environmental insult. The MAP kinases ERK1 and ERK2 respond to signals leading to growth and differentiation. The related MAP kinase p38 and other homologs are involved in stress responses. MAP kinase family members each have a unique constellation of interactions with substrates and upstream activators that assure faithful signaling. We previously determined the structures of the low activity forms of ERK2 and p38, and the active form of ERK2. We will continue our structural studies of this family, and will analyze the interactions of MAP kinases with peptides and full-length proteins to determine the structural basis for selective interactions of the MAP kinases ERK2 and p38 toward transcription factors and protein kinase substrates. We discovered that ERK2 dimerizes when phosphorylated, and the structure of active ERK2 revealed a dimer. Many MAP kinase substrates are dimers. Dimerization is ubiquitous in signaling processes, and may contribute significantly to correct targeting of signals by improving selectivity for the correct substrates. In this study, we will carry out kinetic analysis of active dimeric ERK2 and an active dimerization- deficient mutant to determine the effect of dimerization on the activity toward transcription factor substrates.