Ser/Thr/Tyr phosphoproteome characterization of Acinetobacter baumannii: Comparison between a reference strain and a highly invasive multidrug-resistant clinical isolate

In the current study, the Ser/Thr/Tyr phosphoproteomes of two Acinetobacter baumannii strains, reference (ATCC17978) and highly invasive multidrug-resistant clinical isolate (Abh12O-A2) were analyzed using SCX and TiO 2 chromatography followed by high resolution mass spectrometry. We detected a total of 201 unique phosphorylation sites (p-sites), and, after manual validation of peptide spectra, 91 high-confidence phosphorylation events (p-events) could be localized to a specific amino acid residue. The percentage distribution of Ser/Thr/Tyr phosphorylation was 68.9% on serine, 24.1% on threonine and 5.2% on tyrosine in ATCC17978, and 70.8% on serine, 25.2% on threonine and 3.8% on tyrosine in AbH12O-A2. Across all identified p-sites, 11 were identified in ATCC17978 only, while 43 were identified in Abh12O-A2 only, and 37 overlapped between the two strains. Here for the first time we describe the phosphoproteome of A. baumanii , and significance of selected phosphorylation sites is discussed in the context of stress/starvation, pathogenicity and drug resistance. Biological significance It is now well established that protein phosphorylation on Ser/Thr/Tyr residues is an important post-translational modification in bacteria. Herein we employed SCX and TiO 2 chromatographic phosphopeptide enrichment combined with LTQ-Orbitrap mass spectrometric analyses to characterize and establish a qualitative comparison between the Ser/Thr/Tyr phosphoproteomes of two Acinetobacter baumannii strains: a reference strain and a highly invasive multidrug-resistant clinical isolate. We highlight the identification of phosphoproteins with a role in pathogenicity and those involved in drug resistance.