Observation of Escherichia coli ribosomal proteins and their posttranslational modifications by mass spectrometry

Ribosomes from the K-12 strain of Escherichia coli were analyzed with good sensitivity and high mass accuracy using matrix-assisted laser desorption/i onization time-of-flight mass spectrometry. Fifty-five of the 56 subunit pr oteins were observable. Mass spectral peak. locations were consistent with previously reported post-translational modifications involving N-terminal m ethionine loss, methylation, thiomethylation, and acetylation for all but o ne case. The speed and accuracy of mass spectrometry make it a good candida te for phylogenetic studies of ribosomes and the observation of posttransla tional modifications in Other organisms. (C) 1999 Academic Press.