Mutational scan inferred binding energetics and structure in intrinsically disordered protein CcdA

Area of Science:

• Biochemistry
• Structural Biology
• Genetics

Background:

• Intrinsically Disordered Proteins (IDPs) lack stable tertiary structures, making their functional mechanisms and mutational effects less understood than globular proteins.
• Understanding sequence-function relationships in IDPs is crucial for deciphering their roles in cellular processes and disease.

Purpose of the Study:

• To investigate the impact of mutations on the function of the CcdA Intrinsically Disordered Protein.
• To develop a high-throughput method for analyzing sequence-function relationships in IDPs.
• To gain insights into the structural determinants of binding affinity in IDPs.

Main Methods:

• Deep Mutational Scanning (DMS) using a yeast surface display mutant library.
• Quantitative estimation of relative binding constants using a single ligand concentration.
• Analysis of mutational sensitivity to predict interface residues and local structural features.

Main Results:

• DMS successfully identified sequence-function relationships for the CcdA IDP.
• The study demonstrates that a single ligand concentration can quantitatively estimate binding affinities for numerous variants.
• Energetic effects of mutations in IDPs are distributed over a smaller range compared to globular proteins.
• Insights were gained into the roles of helicity and disorder in IDP-partner interactions.

Conclusions:

• Deep mutational scanning is an effective approach for studying IDPs.
• The findings provide a foundation for predicting how mutations affect IDP binding affinity.
• This work contributes to understanding the complex interplay of disorder, structure, and function in IDPs.