A method to define the carboxyl terminal of proteins.
Accurate definition of the carboxyl terminal of proteins is necessary for elucidating posttranslational processing at the C-terminal and more generally for characterizing protein primary structures. Here, we describe a strategy for isolating and characterizing the C-terminal peptide of a protein after proteolysis with endoprotease Lys-C. Isolation is achieved using anhydrotrypsin, a catalytically inert derivative of trypsin that binds peptides containing lysine or arginine residues at their C-termini without cleaving them. Rapid, accurate characterization of the isolated C-terminal peptide is achieved by mass spectrometry. Initial identification of the C-terminal peptide is obtained by comparing matrix-assisted laser desorption/ionization time-of-flight mass spectra of the digest prior to and after incubation with anhydrotrypsin. Characterization of the C-terminal sequence is achieved by capillary-HPLC electrospray ionization tandem mass spectrometry of the isolated peptide using a quadrupole ion trap mass spectrometer in the selective reaction monitoring mode. This strategy was successfully applied to the characterization of the C-terminal of proteins with molecular masses ranging up to 56 kDa.
Sechi
S
S
Laboratory for Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, New York 10021, USA.
Chait
B T
BT
D007202:Indicators and Reagents; D010455:Peptides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D007202:Indicators and Reagents; D010455:Peptides; D011506:Proteins