Lysine Trimethylation in Planktonic and Pellicle Modes of Growth in Acinetobacter baumannii .

Over the past 30 years, has been described as an important nosocomial pathogen due to frequent ventilator-associated infections. Many biological processes of remain elusive, such as the formation of an air-liquid biofilm (pellicle). Several studies demonstrated the importance of post-translational modifications (PTMs) in physiology. Here, we investigated K-trimethylation in ATCC 17978 in planktonic and pellicle modes using proteomic analysis. To identify the most high-confidence K-trimethylated peptides, we compared different sample preparation methods (i.e., strong cation exchange, antibody-capture) and processing software (i.e., different database search engines). We identified, for the first time, 84 K-trimethylated proteins, many of which are involved in DNA and protein synthesis (HupB, RplK), transporters (Ata, AdeB), or lipid metabolism processes (FadB, FadD). In comparison with previous studies, several identical lysine residues were observed acetylated or trimethylated, indicating the presence of proteoforms and potential PTM cross-talks. This is the first large-scale proteomic study of trimethylation in and will be an important resource for the scientific community (availability in Pride repository under accession PXD035239).