A strategy for the rapid identification of phosphorylation sites in the phosphoproteome.


Journal Article

Edman phosphate ((32)P) release sequencing provides a high sensitivity means of identifying phosphorylation sites in proteins that complements mass spectrometry techniques. We have developed a bioinformatic assessment tool, the cleavage of radiolabeled protein (CRP) program, which enables experimental identification of phosphorylation sites via (32)P labeling and Edman degradation of cleaved proteins obtained at femtomole levels. By observing the Edman cycle(s) in which radioactivity is found, candidate phosphorylation sites are identified by determining which residues occur at the observed number of cycles downstream from a peptide cleavage site. In cases where more than one residue could be responsible for the observed radioactivity, additional experiments with cleavage reagents having alternative specificities may resolve the ambiguity. Given a protein sequence and a cleavage site, CRP performs these experiments in silico, identifying resolved sites based on user-supplied experimental data, as well as suggesting combinations of reagents for additional analyses. Analysis of the PhosphoBase protein sequence database suggests that CRP data from two cleavage experiments can be used to identify unambiguously 60% of known phosphorylation sites. Data from additional cleavage experiments may increase the overall coverage to 70% of known sites. By comparing theoretical data obtained from the CRP program with (32)P release data obtained from an Edman sequencer, a known phosphorylation site was identified unambiguously and correctly. In addition, our results show that in vivo phosphorylation sites can be determined routinely by differential proteolysis analysis and Edman cycling with less than 1 fmol of protein and 1000 cpm.

Full Text

Duke Authors

Cited Authors

  • MacDonald, JA; Mackey, AJ; Pearson, WR; Haystead, TAJ

Published Date

  • April 2002

Published In

Volume / Issue

  • 1 / 4

Start / End Page

  • 314 - 322

PubMed ID

  • 12096113

Pubmed Central ID

  • 12096113

International Standard Serial Number (ISSN)

  • 1535-9476

Digital Object Identifier (DOI)

  • 10.1074/mcp.m200002-mcp200


  • eng

Conference Location

  • United States