Acetonitrile-induced unfolding of the photosystem II manganese-stabilizing protein studied by electrospray mass spectrometry

In this paper an acetonitrile‐induced unfolding of the manganese‐stabilizing protein (MSP) of photosystem II was discovered. More distinct unfolding states of MSP were identified than previously by using mainly electrospray ionization mass spectrometry (ESI‐MS), together with fluorescence spectra an...

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Bibliographic Details
Published in:Rapid communications in mass spectrometry 2005-01, Vol.19 (15), p.2151-2156
Main Authors: Zhang, Li, Zhang, Feng, Zhang, Su-Yan, Guo, Yin-Long, Xu, Chun-He
Format: Article
Language:English
Subjects:
Acetonitriles - chemistry
Manganese - chemistry
Photosystem II Protein Complex - chemistry
Plant Proteins - chemistry
Protein Folding
Spectrometry, Mass, Electrospray Ionization - methods
Spinacia oleracea - chemistry
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Summary:In this paper an acetonitrile‐induced unfolding of the manganese‐stabilizing protein (MSP) of photosystem II was discovered. More distinct unfolding states of MSP were identified than previously by using mainly electrospray ionization mass spectrometry (ESI‐MS), together with fluorescence spectra and far‐UV circular dichroism (CD) at pH 2.0, 6.2 or 11.6, and with acetonitrile concentrations from 0 to 50%. At pH 6.2 with acetonitrile concentration changing from 0 to 10%, relatively broad charge‐state distributions and poor intensity were observed in ESI‐MS, indicating the presence of coexisting conformers. It was concluded that the structure of the MSP protein is unlikely to be a tightly folded form. When the concentration of acetonitrile was 20–40%, simulating the state in the biological membrane, changes in the state of unfolding of MSP were observed to a certain extent using ESI‐MS, fluorescence and CD spectroscopy. The charge‐state distribution in ESI‐MS was found to move toward high states (from 13+ to 27+ to 15+ to 31+) with increasing acetonitrile concentration. At pH 2.0, the MSP structure is rearranged into an unfolded state, and at pH 11.6 the MSP structure is induced to assume another unordered state by deprotonation of appropriate residues. An interesting observation was that a second peak envelope emerged with 20–50% acetonitrile in the medium at pH 11.6. Copyright © 2005 John Wiley & Sons, Ltd.
ISSN:0951-4198
1097-0231
DOI:10.1002/rcm.2043