A conserved dimerization element is required for protein kinase activation by trans-autophosphorylation

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Protein kinases are a large enzyme family crucial in human biology and disease.
• Most protein kinases activate via trans-autophosphorylation, a process involving dimerization and mutual phosphorylation.
• The structural basis for kinase dimerization and activation has remained incompletely understood.

Purpose of the Study:

• To investigate the conserved structural mechanisms underlying trans-autophosphorylation dimerization in human kinases.
• To identify common structural elements involved in kinase activation through dimerization.
• To explore the evolutionary origins of kinase dimerization mechanisms.

Main Methods:

• Systematic screening of all human kinase crystal structures for compatible trans-autophosphorylation dimers.
• Mutagenesis studies on key kinases to validate the role of identified structural elements in dimerization and activation.
• Biochemical assays to assess dimerization and autophosphorylation in purified kinase domains and full-length proteins in cellular contexts.

Main Results:

• Identified 655 potential trans-autophosphorylation dimers from 143 human kinases.
• Discovered that 85% of these dimers bury the same helix, αG, at the dimer interface.
• Demonstrated that αG substitution impairs or abolishes kinase activation in all tested kinases, both in vitro and in cells.
• Showed that αG-mediated dimers lack a conserved structural arrangement, despite the conserved interface element.

Conclusions:

• Dimerization during trans-autophosphorylation is a conserved process in the human kinome.
• The αG helix is a critical, conserved structural element mediating kinase dimerization and activation across species.
• Kinase activation via αG-mediated dimerization is conserved, but allows for diverse relative orientations of the kinase domains.