Synthesis of multi-unit protein hetero-complexes in the gas phase via ion–ion chemistry
Version of Record online: 8 JUN 2004
Copyright © 2004 John Wiley & Sons, Ltd.
Journal of Mass Spectrometry
Volume 39, Issue 6, pages 630–638, June 2004
How to Cite
Gunawardena, H. P. and McLuckey, S. A. (2004), Synthesis of multi-unit protein hetero-complexes in the gas phase via ion–ion chemistry. J. Mass Spectrom., 39: 630–638. doi: 10.1002/jms.629
- Issue online: 8 JUN 2004
- Version of Record online: 8 JUN 2004
- Manuscript Accepted: 29 JAN 2004
- Manuscript Received: 2 DEC 2003
- US Department of Energy, Office of Basic Sciences. Grant Number: DE-FG02-00ER15105.
- ion–ion reactions;
- protein complexes
The synthesis of protein hetero-complex ions via ion–ion reactions in the gas phase is demonstrated in a quadrupole ion trap. Bovine cytochrome c cations and bovine ubiquitin anions are used as reactant species in the stepwise construction of complexes containing as many as six protein sub-units. For any set of reactants, a series of competitive and consecutive reactions is possible. The yield of complex ions for any given sequence of reactions is primarily limited by the presence of competitive reactions. Proton transfer represents the most important competitive reaction that adversely affects protein complex synthesis. In the present data, proton transfer takes place most extensively in the first step of complex synthesis, when single protein sub-units are subjected to reaction with one another. Proton transfer is found to be less extensive when one of the reactants is a protein complex. The generation of hexameric hetero-complexes containing two cytochrome c molecules and four ubiquitin molecules is demonstrated with two different synthesis approaches. The first involved the initial reaction of several charge states of cytochrome c and several charges states of ubiquitin. The sequence of reactions in this example illustrates the array of possible competitive and consecutive reactions associated with even a relatively simple set of multiply charged reactants. The second approach involved the initial reaction of the 9+ charge state of cytochrome c and the 5− charge state of ubiquitin. The latter approach highlights the utility of the multi-stage mass spectrometric (MSn) capabilities of the ion trap in defining reactant ion identities (i.e. charge states and polarities) so that synthesis reactions can be directed along a particular set of pathways. Copyright © 2004 John Wiley & Sons, Ltd.