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

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).

Intrinsically Disordered Flanking Regions Increase the Affinity of a Transcriptional Coactivator Interaction across Vertebrates

“…It has become clear that protein interaction and stability depend on context including regions outside of the “canonical” binding site. ,,,− Emerging quantitative data suggest a role of disordered flanking regions, which could make multiple transient interactions with a folded interaction partner to either increase or decrease affinity. ,, Phylogenetic methods are powerful in pinpointing evolutionarily conserved regions in proteins. If these regions are involved in a protein–protein interaction, then the conserved residues are likely important for affinity and specificity.…”

Characterization of the Conformations of Amyloid Beta 42 in Solution That May Mediate Its Initial Hydrophobic Aggregation

“…This hydrophobic collapse can occur as a consequence of the increase in free energy or the increase in temperature, both of which results in a decrease in enthalpy. Such reduction in enthalpy has been shown to increase protein stability. , …”

“…Such reduction in enthalpy has been shown to increase protein stability. 90,91 Another interesting and important pattern in relation to the solvent accessibility and the change in conformational free energy can be observed. Although, on average, as conformations become more structured and less hydrophobic as the free energy increases (Figures 5, 6 and 8), the broader distribution of HI values suggests that a significant proportion of high free energy (in the 10−25 kJ/mol range) structured conformations retain a substantial hydrophobic character compared to those sampled at the lower free energy range (<10 kJ/mol) (Figure 8).…”

Expression, Purification, Characterization and Cellular Uptake of MeCP2 Variants

“…As mentioned, the full-length MeCP2 as well as their eGFP fusion variants were found to possess an abnormally large hydrodynamic radius for a globular protein of their size, consistent with previous studies [ 26 ]. Other work has shown that while the structured MeCP2 domains such as the MBD possess a radius consistent with that of globular protein, a MeCP2 protein construct that harbors this domain along with its disordered flanking regions, has a very significantly enlarged radius of 5.5 nm [ 29 ]. This further shows the degree of disorder that the random coil portions of MeCP2 impart on structured domains such as well as on the overall protein conformation.…”