Determination of disulphide bridges in PG-2, an antimicrobial peptide from porcine leukocytes

J Pept Sci. 1995 May-Jun;1(3):207-15. doi: 10.1002/psc.310010308.


We determined the cysteine connectivity of protegrin PG-2, a leukocyte-derived antimicrobial peptide, by performing sequential enzyme digestions with chymotrypsin and thermolysin, and monitoring each digest by direct liquid chromatography-electrospray mass spectrometric analysis. This approach resolved the disulphide pairing pattern unambiguously with only picomolar amounts of PG-2. The inferred cysteine connectivity was confirmed by traditional amino acid composition analyses using nanomolar amounts of the protegrin. The results suggest that protegrins will assume a tachyplesin-like, disulphide-stabilized anti-parallel beta-sheet configuration in solution.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acids / analysis
  • Animals
  • Anti-Infective Agents / chemistry*
  • Anti-Infective Agents / isolation & purification
  • Antimicrobial Cationic Peptides
  • Chromatography, High Pressure Liquid
  • Chymotrypsin
  • Cysteine / chemistry
  • Disulfides / chemistry
  • Leukocytes / cytology
  • Mass Spectrometry
  • Molecular Structure
  • Protein Structure, Secondary
  • Proteins / chemistry*
  • Proteins / isolation & purification
  • Solutions
  • Swine
  • Thermolysin


  • Amino Acids
  • Anti-Infective Agents
  • Antimicrobial Cationic Peptides
  • Disulfides
  • Proteins
  • Solutions
  • protegrin-2
  • Chymotrypsin
  • Thermolysin
  • Cysteine