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| Michael Sattler - Structural and Computational Biology Unit & Gene Expression | |
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Michael Sattler
European Molecular Biology Laboratory, Heidelberg, Germany
Structural characterization of multi-domain proteins and macromolecular complexes that play important roles in the regulation of cellular functions is a current challenge in structural biology. Crystallization of such complexes is not always easily accomplishable and even if successful, quaternary arrangements may be affected by crystal packing, especially when flexible linkers and weaker domain interactions are involved.
Small angle X-ray or neutron scattering (SAS) can provide information about the radius of gyration and <<shape>> of such complexes in solution. Additional information can be obtained by deuterium labeling of individual domains and/or subunits and contrast matching in small angle neutron scattering (SANS) experiments. However, often ambiguities remain of how to position high-resolution domain structures within the low resolution envelopes of the complex envelopes.
In the past decade, developments in sample preparation, NMR instrumentation and NMR methodology have dramatically facilitated solution state NMR studies of biomacromolecules with increasing molecular weight. Residual dipolar couplings (RDCs) measured by nuclear magnetic resonance (NMR) in solution can provide powerful orientational restraints that define domain orientations but suffer from the inability to provide translational restraints, such as inter-domain distances or radii of gyration. In addition, NMR chemical shift mapping experiments and paramagnetic relaxation enhancements (PRE) from spin-labeling can provide information about molecular interfaces within a complex. These NMR parameters (chemical shifts, RDC, PRE) can be measured for molecular weights up to 100 kDa and beyond and are thus very complementary to SAS data for structural analysis.
The utility of combining NMR orientational restraints and SAS translational restraints has been explored in the past few years. Such approaches will be presented and discussed and the utility demonstrated with examples from multidomain proteins and protein complexes.
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