Characterizing protein glycosylation sites through higher-energy C-trap dissociation
Article first published online: 30 MAR 2010
Copyright © 2010 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 24, Issue 9, pages 1217–1225, 15 May 2010
How to Cite
Segu, Z. M. and Mechref, Y. (2010), Characterizing protein glycosylation sites through higher-energy C-trap dissociation. Rapid Commun. Mass Spectrom., 24: 1217–1225. doi: 10.1002/rcm.4485
- Issue published online: 7 APR 2010
- Article first published online: 30 MAR 2010
- Manuscript Accepted: 25 JAN 2010
- Manuscript Revised: 23 DEC 2009
- Manuscript Received: 28 SEP 2009
Assigning glycosylation sites of glycoproteins and their microheterogeneity is still a very challenging analytical task despite the rapid advancements in mass spectrometry. It is shown here that glycopeptide ions can be fragmented efficiently using the higher-energy C-trap dissociation (HCD) feature of a linear ion trap orbitrap hybrid mass spectrometer (LTQ Orbitrap). An attractive aspect of this dissociation option is the generation of distinct Y1 ions (peptide+GlcNAc), thus allowing unequivocal assignment of N-glycosylation sites of glycoproteins. The combination of the very informative collision-induced dissociation spectra acquired in the linear ion trap with the distinct features of HCD offers very useful information aiding in the characterization of the glycosylation sites of glycoproteins. The HCD activation energy needed to obtain optimum Y1 ions was studied in terms of glycan structure and charge state, and size and structure of the peptide backbone. The latter appeared to be primarily dictating the needed HCD energy. The distinct Y1 ion formation in HCD facilitated an easy assignment of such an ion and its subsequent isolation and dissociation through multiple-stage tandem mass spectrometry. The resulting MS3 spectrum of the Y1 ion facilitates database searching and denovo sequencing thus prompting the subsequent identification of the peptide backbone and associated glycosylation sites. Moreover, fragment ions formed by HCD are detected in the Orbitrap, thus overcoming the 1/3 cut-off limitation that is commonly associated with ion trap mass spectrometers. As a result, in addition to the Y1 ion, the common glycan oxonium ions are also detected. The high mass accuracy offered by the LTQ Orbitrap mass spectrometer is also an attractive feature that allows a confident assignment of protein glycosylation sites and the microheterogeneity of such sites. Copyright © 2010 John Wiley & Sons, Ltd.