Disordered Domain Shifts the Conformational Ensemble of the Folded Regulatory Domain of the Multidomain Oncoprotein...

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biophysics

Background:

• c-Src kinase is a key regulator of cell signaling, often dysregulated in cancers.
• Its regulatory domains (SH3-SH2) and catalytic domain are well-studied, but the N-terminal disordered region (SH4UD) remains poorly understood.
• Understanding SH4UD's role is crucial for deciphering c-Src's aberrant function in disease.

Purpose of the Study:

• To investigate the structural interactions between the SH4UD and the SH3-SH2 domains of c-Src kinase.
• To elucidate how the disordered SH4UD influences the conformation and dynamics of the folded SH3-SH2 domains.
• To provide molecular insights into the allosteric regulation of c-Src kinase.

Main Methods:

• Domain-selective isotopic labeling combined with small-angle neutron scattering (SANS) contrast matching.
• Hamiltonian replica exchange molecular dynamics (HREX MD) simulations.
• Analysis of changes in radius of gyration (Rg) and domain conformational dynamics.

Main Results:

• The presence of SH4UD led to an increased radius of gyration (Rg) of the SH3-SH2 domains, indicating a more extended conformation.
• HREX MD simulations revealed significant conformational changes in the regulatory loops of the SH3 domain upon SH4UD interaction.
• The SH2 domain's structure remained largely unaffected by the SH4UD, while SH3 exhibited increased flexibility.

Conclusions:

• The disordered SH4UD actively modulates the conformation and flexibility of the folded SH3-SH2 regulatory domains in c-Src kinase.
• This interaction highlights a mechanism where intrinsically disordered regions can induce allosteric changes in folded protein domains.
• These findings offer potential therapeutic strategies targeting c-Src's regulatory domains for cancer treatment.