β-Methylthio-aspartic acid: Identification of a novel posttranslational modification in ribosomal protein S12 from Escherichia coli

Abstract

Utilizing microscale chemical derivatization reactions and matrix- assisted laser desorption/ionization time-of-flight mass spectrometry, we have identified a novel posttranslational modification of aspartic acid, β- methylthio-aspartic acid. The modified residue is located at position 88 in ribosomal protein S12 from Escherichia coli, a phylogenetically conserved protein that has been implicated in maintaining translational accuracy of the ribosome.