Stabilization Effect of Intrinsically Disordered Regions on Multidomain Proteins: The Case of the Methyl-CpG Protein 2, MeCP2.

David Ortega-Alarcon,Olga C. Jorge-Torres,Manel Esteller,Rafael Claveria-Gimeno,Sonia Vega,Olga Abian,Adrian Velazquez-Campoy

doi:10.3390/biom11081216

Abstract

Intrinsic disorder plays an important functional role in proteins. Disordered regions are linked to posttranslational modifications, conformational switching, extra/intracellular trafficking, and allosteric control, among other phenomena. Disorder provides proteins with enhanced plasticity, resulting in a dynamic protein conformational/functional landscape, with well-structured and disordered regions displaying reciprocal, interdependent features. Although lacking well-defined conformation, disordered regions may affect the intrinsic stability and functional properties of ordered regions. MeCP2, methyl-CpG binding protein 2, is a multifunctional transcriptional regulator associated with neuronal development and maturation. MeCP2 multidomain structure makes it a prototype for multidomain, multifunctional, intrinsically disordered proteins (IDP). The methyl-binding domain (MBD) is one of the key domains in MeCP2, responsible for DNA recognition. It has been reported previously that the two disordered domains flanking MBD, the N-terminal domain (NTD) and the intervening domain (ID), increase the intrinsic stability of MBD against thermal denaturation. In order to prove unequivocally this stabilization effect, ruling out any artifactual result from monitoring the unfolding MBD with a local fluorescence probe (the single tryptophan in MBD) or from driving the protein unfolding by temperature, we have studied the MBD stability by differential scanning calorimetry (reporting on the global unfolding process) and chemical denaturation (altering intramolecular interactions by a different mechanism compared to thermal denaturation).

Highlights

Disordered proteins (IDP) and intrinsically disordered regions (IDR) are involved in many physiological mechanisms and pathologies
Disorder increases the structural plasticity and flexibility, allowing proteins to adopt multiple conformations within a complex conformational landscape depending on the environmental conditions, which is important for interacting with many biological partners [4,5] (IDPs or proteins containing IDRs represent important hubs in metabolic and signaling networks) and undergoing conformational changes required for cellular trafficking, internalization, and degradation [6,7]
In order to rule out these possibilities, we studied the unfolding of methylbinding domain (MBD)

Summary

Introduction

Disordered proteins (IDP) and intrinsically disordered regions (IDR) are involved in many physiological mechanisms and pathologies. IDPs and IDRs contain a large proportion of polar, hydrophilic residues, compared to well-folded proteins and regions, which provide them the capability of populating a dynamic, rich ensemble of structures [1,2] They do not fold spontaneously into a stable conformation in aqueous solvent because they lack a hydrophobic core or it is insufficiently large, but they are usually very susceptible to environmental factors (e.g., presence of ligands and interacting macromolecules, redox state, or pH of the surroundings) and posttranslational modifications [3]. Disorder makes some regions more susceptible to posttranslational modifications [8], which represents another protein regulation level conditioning the accessible conformations and the potential interactions with other biomolecules

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Discussion

Conclusion