Sulfolobus islandicus HCD+ETD, including LFQ

Protein posttranslational methylation and acetylations have been reported to occur in archaea, including members of the genus Sulfolobus, but have not been characterized on a proteome-wide scale. Sulfolobus chromatin proteins are known to be methylated and acetylated on lysine side chains, resembling eukaryotic histones in this respect. We utilized bottom-up and top-down proteomic approaches to perform a global and deep methylation study in the hyperthermoacidophylic archaeon S. islandicus LAL 14/1 with a particular focus on chromatin proteins. Without specific enrichment, 1931 methylation sites on 731 protein were found by bottom-up proteomic analysis. The dynamics of protein methylation has been investigated on 424-526 proteins throughout 3 cell culture growth stages. We also confirm the relaxed specificity and steady abundance of the previously described methyltransferase aKMT4 which is implicated in the massive proteome methylation. We also detected an abundant N-terminal acetylation of S. islandicus proteins, with more than one third of the detected N-terminal peptides being acetylated