The Balancing Act of Intrinsically Disordered Proteins: Enabling Functional Diversity while Minimizing Promiscuity

Area of Science:

• Biochemistry
• Molecular Biology
• Systems Biology

Background:

• Intrinsically disordered proteins (IDPs) and regions (IDRs) are crucial for cellular functions but can cause promiscuous interactions.
• The cellular environment presents challenges for IDRs, necessitating adaptive mechanisms for functional diversity and interaction specificity.

Purpose of the Study:

• To investigate how intrinsically disordered regions (IDRs) adapt to enable functional diversity while minimizing promiscuous interactions in the crowded cellular environment.
• To explore the relationship between IDR content, amino acid composition, protein concentration, and interaction networks in Saccharomyces cerevisiae.

Main Methods:

• Analysis of protein sequences, predicted intrinsic disorder, and 3D structure content in yeast (Saccharomyces cerevisiae).
• Integration of data on protein cellular concentrations, gene co-expression, and protein-protein interactions.
• Clustering analysis of Gene Ontology terms to identify multifunctional proteins.

Main Results:

• Protein IDR content and "sticky" amino acid frequency decrease with increasing cellular concentration, indicating negative selection.
• Higher IDR content correlates with more interactions with other IDR-containing partners and greater functional diversity of partners.
• Multifunctional proteins are enriched in IDRs, featuring more "sticky" amino acids in their IDRs compared to non-multifunctional proteins or structured protein surfaces.

Conclusions:

• IDR content and composition are under selection pressure related to protein concentration to balance functional diversity and interaction specificity.
• IDRs play a significant role in mediating interactions for multifunctional proteins, facilitating diverse and specific binding events.
• The properties of IDRs, particularly in multifunctional proteins, are finely tuned to achieve binding affinity and counteract entropic losses upon interaction.