Title
Subunit exchange of multimeric protein complexes : real-time monitoring of subunit exchange between small heat shock proteins by using electrospray mass spectrometry
Author
Faculty/Department
Faculty of Sciences. Chemistry
Publication type
article
Publication
Baltimore, Md ,
Subject
Chemistry
Source (journal)
Journal of biological chemistry. - Baltimore, Md
Volume/pages
277(2002) :41 , p. 38921-38929
ISSN
0021-9258
ISI
000178529600115
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Abstract
The subunit exchange of the small heat shock proteins (sHSPs) PsHSP18.1 from pea andTaHSP16.9 from wheat has been monitored in real-time using nanoelectrospray mass spectrometry. By preserving the noncovalent interactions between subunits in the mass spectrometer, we show that these proteins are dodecameric. After mixing PsHSP18.1 andTaHSP16.9, a distribution of heterododecamers is formed. A comparison with spectra obtained from statistical modeling demonstrates that after equilibration the distribution of these heterocomplexes is governed by the starting ratio of the two components rather than an inherent preference for certain stoichiometries. This finding suggests that the two different sHSP subunits interact in a very similar manner. Following the kinetics of this reaction by mass spectrometry reveals that exchange proceeds via sequential incorporation of subunits with dimeric species being the principal units of exchange. Therefore, we conclude that sHSP complexes are in rapid dissociation/reassociation equilibria with suboligomeric forms. More generally, these experiments illustrate a powerful approach for the real-time analysis of the evolution of transient species and their relative populations during the subunit exchange of multimeric protein complexes.
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