Alanine and proline content modulate global sensitivity to discrete perturbations in disordered proteins

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Biological signal transduction often relies on protein structural changes.
• Intrinsically disordered proteins (IDPs) play crucial roles in signaling pathways.
• The mechanism by which IDPs couple local to global structural changes is not fully understood.

Purpose of the Study:

• To investigate the ability of intrinsically disordered proteins to link local structural modifications to global structural alterations.
• To explore the role of specific amino acid residues in modulating these structure-function relationships in IDPs.

Main Methods:

• Utilized the N-terminal region of the p53 protein as an intrinsically disordered protein model.
• Created proline (PRO) and alanine (ALA) to glycine (GLY) substitution variants to alter backbone conformational propensities.
• Employed circular dichroism spectroscopy and fluorescence methods to assess structural changes.
• Measured hydrodynamic radius (R(h)) to monitor global structural changes.
• Performed molecular simulations to model experimental findings and assess generality.

Main Results:

• Glycine substitutions reduced polyproline II (PP(II)) propensities in IDPs.
• Substitution-induced changes in R(h) were not linked to protein folding.
• Local alterations in PP(II) structure correlated with variable changes in R(h).
• The observed effects depended on the inherent chain propensities of PRO and ALA residues.

Conclusions:

• Demonstrated a mechanism for coupling local and global structure changes in intrinsically disordered proteins.
• Highlighted the significant influence of proline and alanine residues on IDP structure and dynamics.
• Suggested that these findings are generalizable to other IDPs and biological systems.