Table I.

Tryptic Peptides Identified by Mass Spectrometry

Position of peptide
 in the polypeptide
 chainMeasured masses
 [M+H]+Calculated masses
 [M+H]+
146-161
   +C2H3ON@Cysa1,677.71,677.8
80–941,722.81,722.9
78–941,965.91,966.0
57–762,131.02,131.1
57-76
   +O@Metb2,147.02,147.1
57-76
   +20@Metc2,163.02,163.1
57–772,259.02,259.1
57-77
   +O@Metb2,275.02,275.1
57-77
   +2O@Metc2,291.02,291.1
104–1232,400.92,401.0
104-123
   +O@Metb2,416.92,417.0
104-123
   +2O@Metc2,432.92,433.0
  • a Carbamidomethylation of cysteine (due to iodoacetamide present in the lysis buffer).

  • b Mono-oxidation of methionine.

  • c Di-oxidation of methione.

  • The six peptides and their derivatives shown in the table fit unequivocally to the WBSCR5 gene product (AAF74978) and covered 30% of its predicted sequence.