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bioRxiv · 10.1101/313767

Substrate binding allosterically relieves autoinhibition of the TRIB1 pseudokinase

Jamieson, S. A.·Ruan, Z.·Burgess, A. E.·Curry, J. R.·McMillan, H. D.·Brewster, J. L.·Dunbier, A. K.·Axtman, A. D.·Natarajan, K.·Mace, P. D.
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Abstract

One Sentence SummarySubstrate binding to Tribbles-homolog 1 (TRIB1) pseudokinase induces allosteric changes that allow formation of a complex with the COP1 ubiquitin ligase.\n\nAbstractThe Tribbles family of pseudokinases recruit substrates to the COP1 ubiquitin ligase for ubiquitination. CCAAT-enhancer binding protein (C/EBP) family transcription factors are crucial Tribbles substrates in adipocyte and myeloid development. Here we show that the TRIB1 pseudokinase can recruit various C/EBP family members, with binding of C/EBP{beta} attenuated by phosphorylation. To explain the mechanism of substrate recruitment, we solved the crystal structure of TRIB1 in complex with C/EBP. TRIB1 undergoes a significant conformational change relative to its substrate-free structure, to bind C/EBP in a pseudo-substrate-like manner. Crucially, substrate binding triggers allosteric changes that link substrate recruitment to COP1 binding, which is consistent with molecular dynamics and biochemical studies. These findings offer a view of pseudokinase regulation with striking parallels to bona fide kinase regulation-- via the activation loop and C-helix--and raise the possibility of small molecules targeting either the activation loop-in, or loop-out, conformations of Tribbles pseudokinases.

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Jamieson, S. A., Ruan, Z., Burgess, A. E., Curry, J. R., McMillan, H. D., Brewster, J. L., Dunbier, A. K., Axtman, A. D., Natarajan, K., Mace, P. D.. 2018-05-03. Substrate binding allosterically relieves autoinhibition of the TRIB1 pseudokinase. https://doi.org/10.1101/313767

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