Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
Mol Cell Biol. 2012 Apr;32(8):1337-53. doi: 10.1128/MCB.06525-11. Epub 2012 Feb 21.
The atypical AGC kinase Greatwall (Gwl) mediates a pathway that prevents the precocious removal of phosphorylations added to target proteins by M phase-promoting factor (MPF); Gwl is thus essential for M phase entry and maintenance. Gwl itself is activated by M phase-specific phosphorylations that are investigated here. Many phosphorylations are nonessential, being located within a long nonconserved region, any part of which can be deleted without effect. Using mass spectrometry and mutagenesis, we have identified 3 phosphorylation sites (phosphosites) critical to Gwl activation (pT193, pT206, and pS883 in Xenopus laevis) located in evolutionarily conserved domains that differentiate Gwl from related kinases. We propose a model in which the initiating event for Gwl activation is phosphorylation by MPF of the proline-directed sites T193 and T206 in the presumptive activation loop. After this priming step, Gwl can intramolecularly phosphorylate its C-terminal tail at pS883; this site probably plays a role similar to that of the tail/Z motif of other AGC kinases. These events largely (but not completely) explain the full activation of Gwl at M phase.
非典型 AGC 激酶 Greatwall（Gwl）介导了一条阻止有丝分裂促进因子（MPF）过早去除靶蛋白磷酸化的途径；因此，Gwl 对于有丝分裂的进入和维持是必不可少的。Gwl 自身通过有丝分裂特异性磷酸化激活，本文对此进行了研究。许多磷酸化是非必需的，它们位于一个长的非保守区域内，该区域的任何部分都可以被删除而没有影响。通过质谱分析和突变，我们确定了 3 个对 Gwl 激活至关重要的磷酸化位点（pT193、pT206 和 pS883），这些位点位于区分 Gwl 与相关激酶的进化保守结构域内。我们提出了一个模型，其中 Gwl 激活的起始事件是 MPF 对假定激活环中的脯氨酸定向位点 T193 和 T206 的磷酸化。在这个启动步骤之后，Gwl 可以在其 C 端尾部自身磷酸化 pS883；该位点可能发挥类似于其他 AGC 激酶的尾部/Z 基序的作用。这些事件在很大程度上（但不是完全）解释了 Gwl 在有丝分裂期的完全激活。
