Mapping proteoforms and protein complexes from king cobra venom using both denaturing and native top-down proteomics

Rafael D. Melani, Owen S. Skinner, Luca Fornelli, Gilberto B. Domont*, Philip D. Compton, Neil L. Kelleher

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Characterizing whole proteins by top-down proteomics avoids a step of inference encountered in the dominant bottom-up methodology when peptides are assembled computationally into proteins for identification. The direct interrogation of whole proteins and protein complexes from the venom of Ophiophagus hannah (king cobra) provides a sharply clarified view of toxin sequence variation, transit peptide cleavage sites and post-translational modifications (PTMs) likely critical for venom lethality. A tube-gel format for electrophoresis (called GELFrEE) and solution isoelectric focusing were used for protein fractionation prior to LC-MS/MS analysis resulting in 131 protein identifications (18 more than bottom-up) and a total of 184 proteoforms characterized from 14 protein toxin families. Operating both GELFrEE and mass spectrometry to preserve non-covalent interactions generated detailed information about two of the largest venom glycoprotein complexes: the homodimeric L-amino acid oxidase (∼130 kDa) and the multichain toxin cobra venom factor (∼147 kDa). The L-amino acid oxidase complex exhibited two clusters of multiproteoform complexes corresponding to the presence of 5 or 6 N-glycans moieties, each consistent with a distribution of N-acetyl hexosamines. Employing top-down proteomics in both native and denaturing modes provides unprecedented characterization of venom proteoforms and their complexes. A precise molecular inventory of venom proteins will propel the study of snake toxin variation and the targeted development of new antivenoms or other biotherapeutics.

Original languageEnglish (US)
Pages (from-to)2423-2434
Number of pages12
JournalMolecular and Cellular Proteomics
Issue number7
StatePublished - Jul 2016

ASJC Scopus subject areas

  • Analytical Chemistry
  • Molecular Biology
  • Biochemistry


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