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Does deamidation cause protein unfolding? A top-down tandem mass spectrometry study
Andrew J Soulby1, Jack W Heal, Mark P Barrow
1Department of Chemistry, University of Warwick, Coventry, United Kingdom.
Protein Science : a Publication of the Protein Society
|February 6, 2015
Summary
Protein deamidation, a modification changing amino acids, can disrupt protein structure and lead to unfolding. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) can effectively study these protein folding changes.
Area of Science:
- Biochemistry
- Structural Biology
- Mass Spectrometry
Background:
- Deamidation is a nonenzymatic post-translational modification converting uncharged asparagine/glutamine to charged aspartic acid/glutamic acid.
- This charge alteration may disrupt protein hydrogen bonding networks, potentially causing protein unfolding.
Purpose of the Study:
- To investigate the impact of deamidation on protein structure and hydrogen bonding networks.
- To evaluate the utility of top-down FTICR-MS for studying deamidation-induced protein folding changes.
Main Methods:
- Calmodulin and B2M proteins were chemically deamidated.
- Tandem mass spectrometry using FTICR-MS was employed to analyze deamidated and non-deamidated protein isoforms.
- Infrared multi-photon dissociation laser power was varied to probe gas-phase hydrogen bonding networks, generating protein unfolding maps.
Main Results:
- Analysis revealed increased fragmentation at lower laser powers near deamidated regions, indicating localized unfolding.
- Decreased fragment intensities across other protein regions suggest strengthened intramolecular interactions due to salt-bridge formation.
- Computational flexibility analysis supported the observed structural effects of deamidation.
Conclusions:
- Deamidation can alter global protein structure by modifying hydrogen bonding networks near modification sites.
- Top-down FTICR-MS is a suitable technique for investigating protein folding dynamics and the effects of post-translational modifications like deamidation.
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