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Concentration Dependent Ion-Protein Interaction Patterns Underlying Protein Oligomerization Behaviours

  • Salts and proteins comprise two of the basic molecular components of biological materials. Kosmotropic/chaotropic co-solvation and matching ion water affinities explain basic ionic effects on protein aggregation observed in simple solutions. However, it is unclear how these theories apply to proteins in complex biological environments and what the underlying ionic binding patterns are. Using the positive ion Ca2+ and the negatively charged membrane protein SNAP25, we studied ion effects on protein oligomerization in solution, in native membranes and in molecular dynamics (MD) simulations. We find that concentration-dependent ion-induced protein oligomerization is a fundamental chemico-physical principle applying not only to soluble but also to membrane-anchored proteins in their native environment. Oligomerization is driven by the interaction of Ca2+ ions with the carboxylate groups of aspartate and glutamate. From low up to middle concentrations, salt bridges between Ca2+ ions and two or more protein residues lead to increasingly larger oligomers, while at high concentrations oligomers disperse due to overcharging effects. The insights provide a conceptual framework at the interface of physics, chemistry and biology to explain binding of ions to charged protein surfaces on an atomistic scale, as occurring during protein solubilisation, aggregation and oligomerization both in simple solutions and membrane systems.

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Document Type:Article
Author:Helena Batoulis, Thomas H. Schmidt, Pascal Weber, Jan-Gero Schloetel, Christian Kandt, Thorsten Lang
Parent Title (English):Scientific Reports
Article Number:24131
Publisher:Nature Research
Publishing Institution:Hochschule Bonn-Rhein-Sieg
Date of first publication:2016/04/07
Funding Information:This work was supported by the Deutsche Forschungsgemeinschaft (SFB645).
Departments, institutes and facilities:Fachbereich Elektrotechnik, Maschinenbau und Technikjournalismus
Dewey Decimal Classification (DDC):5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Entry in this database:2016/04/14
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International