Intra- versus intermolecular interactions in monellin: Contribution of surface charges to protein assembly

Research output: Contribution to journalArticle


The relative significance of weak non-covalent interactions in biological context has been much debated. Here, we have addressed the contribution of Coulombic interactions to protein stability and assembly experimentally. The sweet protein monellin, a non-covalently linked heterodimeric protein, was chosen for this study because of its ability to spontaneously reconstitute from separated fragments. The reconstitution of monellin mutants containing large surface charge perturbations was compared to the thermostability of structurally equivalent single-chain monellin containing the same sets of mutations under varying salt concentrations. The affinity between monellin fragments is found to correlate with the thermostability of single chain monellin, indicating the involvement of the same underlying Coulombic interactions. This confirms that there are no principal differences in the interactions involved in folding and binding. Based on comparison with a previous mutational study involving hydrophobic core residues, the relative contribution of Coulombic interactions to stability and affinity is modest. However, the Coulombic perturbations only affect the association rates of reconstitution in contrast to perturbations involving hydrophobic residues, which affect primarily the dissociation rates. These results indicate that Coulombic interactions are likely to be of main importance for the association of protein assembly, relevant for functions of proteins. (c) 2006 Elsevier Ltd. All rights reserved.


  • Wei-Feng Xue
  • Olga Szczepankiewicz
  • Mikael Bauer
  • Eva Thulin
  • Sara Linse
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Chemistry


  • interactions, electrostatic, protein reconstitution, fragment complementation, global analysis, protein folding and binding
Original languageEnglish
Pages (from-to)1244-1255
JournalJournal of Molecular Biology
Issue number5
Publication statusPublished - 2006
Publication categoryResearch