c-Abl Tyrosine Kinase Adopts Multiple Active Conformational States in Solution

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Protein tyrosine kinases of the Abl family regulate cellular processes and are implicated in leukemia.
• The inactive c-Abl kinase core adopts a compact structure stabilized by intramolecular interactions.
• Mutations disrupting these interactions can lead to kinase activation.

Purpose of the Study:

• To investigate the structural basis of c-Abl kinase activation in different mutant forms.
• To model diverse active states of the multidomain c-Abl kinase core using X-ray scattering.
• To understand the role of global allosteric changes in Abl kinase activation.

Main Methods:

• X-ray scattering (SAXS) to determine solution structures.
• Analysis of multidomain c-Abl kinase core proteins.
• Comparison of wild-type and mutant (A356N, T315I) structures.

Main Results:

• The A356N mutant, an active myristic acid binding pocket mutant, showed minimal changes in domain positioning compared to the wild-type inactive state.
• The T315I mutant, a clinically relevant imatinib-resistant gatekeeper mutant, exhibited reconfigured SH2 and SH3 domain positions.
• Abl kinase activation can occur with or without significant global allosteric changes in the core structure.

Conclusions:

• Abl kinase activation does not always necessitate a dramatic reorganization of the inactive core structure.
• The T315I mutation suggests a mechanism of activation involving global allosteric changes.
• These findings reveal potential for diverse signaling pathways mediated by c-Abl kinase activation states.