Internal nanosecond dynamics in the intrinsically disordered myelin basic protein

Andreas M. Stadler, Laura Stingaciu, Aurel Radulescu, Olaf Holderer, Michael Monkenbusch, Ralf Biehl, Dieter Richter

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

Intrinsically disordered proteins lack a well-defined folded structure and contain a high degree of structural freedom and conformational flexibility, which is expected to enhance binding to their physiological targets. In solution and in the lipid-free state, myelin basic protein belongs to that class of proteins. Using small-angle scattering, the protein was found to be structurally disordered similar to Gaussian chains. The combination of structural and hydrodynamic information revealed an intermediary compactness of the protein between globular proteins and random coil polymers. Modeling by a coarse-grained structural ensemble gave indications for a compact core with flexible ends. Neutron spin-echo spectroscopy measurements revealed a large contribution of internal dynamics to the overall diffusion. The experimental results showed a high flexibility of the structural ensemble. Displacement patterns along the first two normal modes demonstrated that collective stretching and bending motions dominate the internal modes. The observed dynamics represent nanosecond conformational fluctuations within the reconstructed coarse-grained structural ensemble, allowing the exploration of a large configurational space. In an alternative approach, we investigated if models from polymer theory, recently used for the interpretation of fluorescence spectroscopy experiments on disordered proteins, are suitable for the interpretation of the observed motions. Within the framework of the Zimm model with internal friction (ZIF), a large offset of 81.6 ns is needed as an addition to all relaxation times due to intrachain friction sources. The ZIF model, however, shows small but systematic deviations from the measured data. The large value of the internal friction leads to the breakdown of the Zimm model.

Original languageEnglish
Pages (from-to)6987-6994
Number of pages8
JournalJournal of the American Chemical Society
Volume136
Issue number19
DOIs
StatePublished - May 14 2014
Externally publishedYes

Funding

FundersFunder number
European Synchrotron Radiation Facility

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