The Kinetic Mechanism of Multisite Phosphorylation of Activating Transcription Factor 2 by c-Jun N-terminal Kinase 2

The mitogen-activated protein kinases (MAPKs) signal transduction pathway has been well studied as a regulator of a wide range of cellular responses. Specifically, the three-kinase cascade that activates activating transcription factor 2 (ATF2) is implicated in cell proliferation, stress responses, and DNA damage repair. 1 While the kinetic mechanism of ATF2 phosphorylation by p38a has been shown to be non-processive, the phosphorylation mechanism of ATF2 by c-Jun N-terminal kinase 2 (JNK2) is currently unknown. 2 Here, we will investigate the steady-state kinetic mechanism of ATF2 phosphorylation by JNK2 by comparing its kinetic profile with a lower-affinity mutant JNK2 (R127A). Our results show that JNK2 (R127A) has a lower affinity for ATF2 (K m = 4.75 µM ± 0.92) with a similar catalytic efficiency (k cat /K m = 25 s -1 µM -1 ) to the wild-type JNK2 (k cat /K m = 20 s -1 µM -1 ). This data helps design future pre-steady-state kinetic experiments to investigate this mechanism further.