Phosphoregulation of Mixed-Lineage Kinase 1 Activity by Multiple Phosphorylation in the Activation Loop
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- 作者：John T. Durkin ; Beverly P. Holskin ; Karla K. Kopec ; Matt S. Reed ; Chrysanthe M. Spais ; Brian M. Steffy ; George Gessner ; Thelma S. Angeles ; Jan Pohl ; Mark A. Ator ; and Sheryl L. Meyer
- 刊名：Biochemistry
- 出版年：2004
- 出版时间：December 28, 2004
- 年：2004
- 卷：43
- 期：51
- 页码：16348 - 16355
- 全文大小：296K
- 年卷期：v.43,no.51(December 28, 2004)
- ISSN：1520-4995
文摘
Mixed-lineage kinase 1 (MLK1) is a mitogen-activated protein kinase kinase kinase capableof activating the c-Jun NH2-terminal kinase (JNK) pathway. Full-length MLK1 has 1104 amino acids anda domain structure identical to MLK2 and MLK3. Immunoblot and mass spectrometry show that MLK1is threonine (and possibly serine) phosphorylated in or near the activation loop. A kinase-dead mutant isnot, consistent with autophosphorylation. Mutation to alanine of any of the four serine or threonine residuesin the activation loop reduces both the activity of the recombinant kinase domain and JNK pathwayactivation driven by full-length MLK1 expressed in mammalian cells. Furthermore, the gel mobility ofthe mutant MLK1s is closer to that of the kinase-dead than wild type, consistent with reducedphosphorylation. Thr312 is the key residue: MLK1[T312A] retains only basal activity (about 1-2% ofwild type), and its gel mobility is indistinguishable from kinase-dead. Thr312 does not suffice, however;phosphorylation of multiple sites is necessary for full activation of MLK1. An activation mechanismconsistent with these data involves phosphorylation of multiple sites in the activation loop, withphosphorylation of Thr312 required for full phosphorylation. This mechanism is broadly similar to thatpreviously reported for MLK3 [Leung, I. W., and Lassam, N. (2001) J. Biol. Chem. 276, 1961-1967],but the key residue differs.