Modified C-terminal peptides identified from CPG70 tryptic digests using the Orbitrap MS with and without the inclusion of 0.2 M glycine in the growth medium.

a The delta mass is the observed mass minus the observed mass of the unmodified (water-cleaved) peptide (KAEDYIEVILDD, 1421.6930 Da). With the exception of the glycine-modified peptide, all observed masses are taken from the untreated sample.b The best match is the metabolite most closely matching the accurate delta mass value using the Metlin database (see Methods). In every case, the best match was a peptide or amino acid. For peptides, the order of amino acids was inferred from the MS/MS data, with the order of bracketed amino acids being uncertain. The mass error (in ppm) associated with this search is provided in the next column.c The intensity of the strongest MS peak, relative to the unmodified reference peak for the untreated sample. The values for the glycine-treated sample are provided in the next column.CPG70 was purified from W50ABK*WbaP.