Conformational landscape adaptations enable processive phosphorylation by Src family kinases.

Area of Science:

• Biochemistry
• Cellular Signaling
• Enzymology

Background:

• Processive phosphorylation by kinases is vital for rapid, multisite modification of signaling hubs, integrating signals in time-sensitive cellular events.
• Achieving processivity requires multiple catalytic cycles before substrate dissociation, necessitating rapid turnover rates.
• Src family kinases are known to processively phosphorylate multisite substrates.

Purpose of the Study:

• To elucidate the mechanism by which Src family kinases achieve processive phosphorylation.
• To identify conformational states within Src family kinases that facilitate efficient catalytic turnover.
• To determine the functional significance of identified conformational states in kinase activity.

Main Methods:

• Nuclear magnetic resonance (NMR) spectroscopy was employed to investigate the conformational dynamics of Src family kinases.
• The study focused on identifying transient intermediate states within the Src conformational ensemble.
• Functional assays were performed to assess the impact of depleting the intermediate state on kinase activity.

Main Results:

• A transient intermediate state was identified within the Src conformational ensemble, located between active and inactive states.
• This intermediate state was found to facilitate rapid release of adenosine diphosphate (ADP) after adenosine triphosphate (ATP) hydrolysis, enhancing catalytic turnover.
• Depletion of this intermediate state significantly impaired processive phosphorylation by Src, Lck, and Hck, leading to functional deficits.

Conclusions:

• The conformational ensemble of Src family kinases includes a specific transient intermediate state essential for their processive phosphorylation capability.
• This intermediate state is critical for efficient catalytic turnover and multisite substrate modification, underpinning kinase function in cellular signaling.
• Understanding this mechanism provides insights into kinase regulation and the integration of cellular signals.