Mapping Hidden Residual Structure within the Myc bHLH-LZ Domain Using Chemical Denaturant Titration

Area of Science:

• Biochemistry
• Structural Biology
• Chemical Biology

Background:

• Intrinsically disordered proteins (IDPs) are crucial for biological regulation and represent key drug targets.
• Studying IDPs using NMR can be challenging due to residual structure formation, leading to poor spectral quality.
• The Myc oncoprotein's bHLH-LZ domain exemplifies IDPs with such spectral limitations.

Purpose of the Study:

• To develop and apply a novel NMR method to overcome spectral limitations in studying IDPs.
• To characterize the conformational landscape and tertiary interactions of the Myc bHLH-LZ domain.
• To map the binding sites of a Myc inhibitor using the developed method.

Main Methods:

• Application of chemical denaturant titration (CDT)-NMR to intrinsically disordered proteins.
• Exploitation of chemical denaturants to disrupt residual structure and analyze IDP conformer exchange.
• Determination of secondary structure propensities and tertiary interactions for all residues.

Main Results:

• CDT-NMR successfully characterized Myc bHLH-LZ secondary structure propensities and tertiary interactions.
• The study revealed novel conformations of Myc not predicted by existing crystal structures.
• The method mapped perturbation sites of the Myc inhibitor 10058-F4 to residual structure regions.

Conclusions:

• CDT-NMR is an effective technique for studying IDPs with challenging NMR properties.
• The findings provide new insights into the conformational dynamics of the Myc bHLH-LZ domain.
• This approach facilitates the structural characterization of IDPs and their interactions with inhibitors for drug discovery.