Assigning in vivo carbamylation and acetylation in human lens proteins using tandem mass spectrometry and database searching

Zee Yong Park, Rovshan Sadygov, Judy M. Clark, John I. Clark, John R. Yates

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


In this paper, we show that ion trap mass spectrometers can differentiate acetylation and carbamylation modifications based on database search results for a lens protein sample. These types of modifications are difficult to distinguish on ion trap instruments because of their lower resolution and mass accuracy. The results were corroborated by using accurate mass information derived from MALDI TOF MS analysis of eluted peptides from a duplicate capillary RPLC separation. Tandem mass spectra of lysine carbamylated peptides were further verified by manual assignments of fragment ions and by the presence of characteristic fragment ions of carbamylated peptides. It was also observed that carbamylated peptides show a strong neutral loss of the carbamyl group in collision induced dissociation (CID), a feature that can be prognostic for carbamylation. In a lens tissue sample of a 67-year-old patient, 12 in vivo carbamylation sites were detected on 7 different lens proteins and 4 lysine acetylation sites were detected on 3 different lens proteins. Among the 12 in vivo carbamylation sites, 9 are novel in vivo carbamylation modification sites. Notably, in vivo carbamylation of γS crystallin, βA4 crystallin, βB1 crystallin, and βB2 crystallin observed in this study have never been reported before.

Original languageEnglish (US)
Pages (from-to)161-173
Number of pages13
JournalInternational Journal of Mass Spectrometry
Issue number1-3
StatePublished - Jan 1 2007
Externally publishedYes


  • Acetylation
  • In vivo carbamylation
  • LC-MS/MS
  • Shotgun proteomics

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry


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