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Ancient origins of allosteric activation in a Ser-Thr kinase

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Science  21 Feb 2020:
Vol. 367, Issue 6480, pp. 912-917
DOI: 10.1126/science.aay9959

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Evolution of a kinase allosteric site

Enzyme activity is often regulated by conformational changes coupled to binding of an effector at an allosteric site, a feature especially important for enzymes involved in signaling cascades. Hadzipasic et al. studied the origins of allosteric regulation of Aurora A, a kinase involved in progression of the eukaryotic cell cycle. Aurora A is allosterically regulated through the binding of an effector protein named TPX2, which also targets the kinase to spindle microtubules. By reconstructing ancestor kinase sequences, they found that TPX2 bound to an early Aurora A but had very weak activation that was gradually strengthened by evolution of an allosteric network within the kinase. An evolutionary advantage from localizing the active protein at the mitotic spindle may have driven the development of this regulatory mechanism.

Science, this issue p. 912

Abstract

A myriad of cellular events are regulated by allostery; therefore, evolution of this process is of fundamental interest. Here, we use ancestral sequence reconstruction to resurrect ancestors of two colocalizing proteins, Aurora A kinase and its allosteric activator TPX2 (targeting protein for Xklp2), to experimentally characterize the evolutionary path of allosteric activation. Autophosphorylation of the activation loop is the most ancient activation mechanism; it is fully developed in the oldest kinase ancestor and has remained stable over 1 billion years of evolution. As the microtubule-associated protein TPX2 appeared, efficient kinase binding to TPX2 evolved, likely owing to increased fitness by virtue of colocalization. Subsequently, TPX2-mediated allosteric kinase regulation gradually evolved. Surprisingly, evolution of this regulation is encoded in the kinase and did not arise by a dominating mechanism of coevolution.

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