A. Positive ion mode MS from α-tubulin (583.m00022) after CNBr cleavage. Identified peptides are labeled with residue numbers from the sequence insert on the figure. The de-tyrosination and glutamylation sites are indicated by double arrows and molecular weight of amino acid residues. Spectra were acquired in linear mode.
B. The C-terminal CNBr and tryptic peptide of α-tubulin shows up to four glutamylations (in the negative mode). The identified peptides from tubulins are labelled using residue numbers. Glutamylation is indicated by double headed arrows. The residue weight of glutamate (129 Da) is indicated above the arrows. 1-4E indicates the number of glutamylations that occurred on each species. Spectra were acquired in reflector mode.