Complementing structural information of modular proteins with small angle neutron scattering and contrast variation
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Many macromolecules in the cell function by forming multi-component assemblies. We have applied the technique of small angle neutron scattering to study a nucleic acid–protein complex and a multi-protein complex. The results illustrate the versatility and applicability of the method to study macromolecular assemblies. The neutron scattering experiments, complementing X-ray solution scattering data, reveal that the conserved catalytic domain of RNase E, an essential ribonuclease in Escherichia coli (E. coli), undergoes a marked conformational change upon binding a 5′monophosphate–RNA substrate analogue. This provides the first evidence in support of an allosteric mechanism that brings about RNA substrate cleavage. Neutron contrast variation of the multi-protein TIM10 complex, a mitochondrial chaperone assembly comprising the subunits Tim9 and Tim10, has been used to determine a low-resolution shape reconstruction of the complex, highlighting the integral subunit organization. It shows characteristic features involving protrusions that could be assigned to the six subunits forming the complex.
KeywordsSmall angle neutron scattering Contrast variation X-ray scattering RNase E Allosteric mechanism TIM10
Small angle neutron scattering
Small angle X-ray scattering
- RNase E
Translocase of the intermembrane space
The work on RNase E was supported by the Wellcome Trust. We thank Martyn Symmons and Martin Moncrieffe for stimulating discussions and invaluable advice. The work on TIM10 was supported by funds from IMBB-FORTH. The ILL and STFC Daresbury Laboratory are acknowledged for beamtime. We are also very grateful to Peter Timmins at the ILL and Michael Haertlein at the ILL-EMBL-PSB Deuteration Laboratory in Grenoble for their excellent support.
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