Ribosomal phosphopeptides identified using LC-MS/MS after IMAC.

M/Z - mass over charge ratio; Z – ion charge. The experimentally found peptide masses correspond to the masses of phosphopeptides with methyl-esterified dicarboxylic and carboxyl-terminal amino acid residues. Lowercase s in the sequences designate phosphorylated serine residues with the superscript numbers corresponding to the amino acid positions.*Peptide RSEs231LAK with one missed cleavage was obtained in separate experiment of limited proteolysis when ribosomal proteins were treated with trypsin for only two hours at 37 °C.