Crystal structure of an inactive Akt2 kinase domain

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Oncology

Background:

• The Akt/Protein Kinase B (PKB) family, comprising three serine/threonine kinase isoforms, plays a critical role in cell survival pathways.
• Dysregulated Akt activity is frequently observed in human malignancies, contributing to uncontrolled cell proliferation and disease progression.

Purpose of the Study:

• To elucidate the structural basis of Akt2 kinase inactivity.
• To identify key structural features that regulate Akt2 enzymatic activity for potential therapeutic targeting in cancer.

Main Methods:

• X-ray crystallography was employed to determine the three-dimensional structure of the inactive, unliganded Akt2 kinase domain.
• Structural analysis focused on identifying unique conformations and intramolecular interactions responsible for the kinase's quiescent state.

Main Results:

• The determined Akt2 structure exhibits a disordered alpha helix C, deviating from typical kinase conformations.
• The activation loop adopts a sterically hindering conformation, impeding ATP and peptide substrate binding.
• An intramolecular disulfide bond within the activation loop and linker region residues occupying the ATP-binding site further stabilize the inactive state.

Conclusions:

• The Akt2 kinase domain possesses intrinsic structural mechanisms that maintain an inactive conformation.
• These unique structural features, including the activation loop's conformation and disulfide bond, are critical determinants of Akt2 regulation.
• Understanding these structural elements provides a foundation for designing specific inhibitors to target aberrant Akt signaling in cancer.