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PKD autoinhibition in trans regulates activation loop autophosphorylation in cis .

Ronja ReinhardtKai HirzelGisela LinkStephan A EislerTanja HägeleMatthew A H ParsonJohn E BurkeAngelika HausserThomas A Leonard
Published in: Proceedings of the National Academy of Sciences of the United States of America (2023)
Phosphorylation is a ubiquitous mechanism by which signals are transduced in cells. Protein kinases, enzymes that catalyze the phosphotransfer reaction are, themselves, often regulated by phosphorylation. Paradoxically, however, a substantial fraction of more than 500 human protein kinases are capable of catalyzing their own activation loop phosphorylation. Commonly, these kinases perform this autophosphorylation reaction in trans , whereby transient dimerization leads to the mutual phosphorylation of the activation loop of the opposing protomer. In this study, we demonstrate that protein kinase D (PKD) is regulated by the inverse mechanism of dimerization-mediated trans -autoinhibition, followed by activation loop autophosphorylation in cis . We show that PKD forms a stable face-to-face homodimer that is incapable of either autophosphorylation or substrate phosphorylation. Dissociation of this trans -autoinhibited dimer results in activation loop autophosphorylation, which occurs exclusively in cis . Phosphorylation serves to increase PKD activity and prevent trans -autoinhibition, thereby switching PKD on. Our findings not only reveal the mechanism of PKD regulation but also have profound implications for the regulation of many other eukaryotic kinases.
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