FIGURE 3.
Mass spectrometric analyses of chymotryptic digest of native EF-P by nano-LC-ESI-MS/MS. A, the MS/MS spectrum of the triply charged ion at m/z 598.32 originated from the peptide segment Ala-23 to Phe-38 with the addition of 128.095 Da at Lys-34. The sequence of the peptide was assigned single-letter amino acid abbreviation based on the fragment ions observed for the peptide segments. N-terminal b ions and C-terminal y ions (including *y = y-H2O) resulting from the amide bond cleavage are labeled. #, addition of 128 Daltons. B, extracted ion chromatograms obtained from native EF-P sample digested by chymotrypsin. Mass values for the triply charged ions representing peptide segment Ala-23 to Phe-38 (A[23–38]F) with or without the addition of 128.095 Da (lysylation) were extracted.