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A Combined Approach Reveals a Regulatory Mechanism Coupling Src’s Kinase Activity, Localization, and Phosphotransferase-Independent Functions

Ahler, Ethan, Register, Ames C., Chakraborty, Sujata, Fang, Linglan, Dieter, Emily M., Sitko, Katherine A., Vidadala, Rama Subba Rao, Trevillian, Bridget M., Golkowski, Martin, Gelman, Hannah, Stephany, Jason J., Rubin, Alan F., Merritt, Ethan A., Fowler, Douglas M., Maly, Dustin J.
Molecular cell 2019 v.74 no.2 pp. 393-408.e20
active sites, catalytic activity, cell biology, enzyme activity, germplasm conservation, mutagenesis, protein kinases
Multiple layers of regulation modulate the activity and localization of protein kinases. However, many details of kinase regulation remain incompletely understood. Here, we apply saturation mutagenesis and a chemical genetic method for allosterically modulating kinase global conformation to Src kinase, providing insight into known regulatory mechanisms and revealing a previously undiscovered interaction between Src’s SH4 and catalytic domains. Abrogation of this interaction increased phosphotransferase activity, promoted membrane association, and provoked phosphotransferase-independent alterations in cell morphology. Thus, Src’s SH4 domain serves as an intramolecular regulator coupling catalytic activity, global conformation, and localization, as well as mediating a phosphotransferase-independent function. Sequence conservation suggests that the SH4 domain regulatory interaction exists in other Src-family kinases. Our combined approach’s ability to reveal a regulatory mechanism in one of the best-studied kinases suggests that it could be applied broadly to provide insight into kinase structure, regulation, and function.