Intracellular Ser/Thr/Tyr phosphoproteome of the oral commensal Streptococcus gordonii DL1

Carolina Robertsson,Zoltan Blum,Gunnel Svensäter,Claes Wickström

doi:10.1186/s12866-020-01944-y

Abstract

BackgroundTo respond and adapt to environmental challenges, prokaryotes regulate cellular processes rapidly and reversibly through protein phosphorylation and dephosphorylation. This study investigates the intracellular proteome and Ser/Thr/Tyr phosphoproteome of the oral commensal Streptococcus gordonii. Intracellular proteins from planktonic cells of S. gordonii DL1 were extracted and subjected to 2D-gel electrophoresis. Proteins in general were visualized using Coomassie Brilliant Blue and T-Rex staining. Phosphorylated proteins were visualized with Pro-Q Diamond Phosphoprotein Gel Stain. Proteins were identified by LC-MS/MS and sequence analysis.ResultsIn total, sixty-one intracellular proteins were identified in S. gordonii DL1, many of which occurred at multiple isoelectric points. Nineteen of these proteins were present as one or more Ser/Thr/Tyr phosphorylated form. The identified phosphoproteins turned out to be involved in a variety of cellular processes.ConclusionNineteen phosphoproteins involved in various cellular functions were identified in S. gordonii. This is the first time the global intracellular Ser/Thr/Tyr phosphorylation profile has been analysed in an oral streptococcus. Comparison with phosphoproteomes of other species from previous studies showed many similarities. Proteins that are consistently found in a phosphorylated state across several species and growth conditions may represent a core phosphoproteome profile shared by many bacteria.

Highlights

To respond and adapt to environmental challenges, prokaryotes regulate cellular processes rapidly and reversibly through protein phosphorylation and dephosphorylation
The sequenced peptides identified by liquid chromatography (LC)-MS/MS can be found in supplemental material (Additional file 1)
23,000/26870 a) Two or more proteins were identified from this spot b) Gene name in the UniProt database as entered for S. gordonii DL1 proteins c) Accession number in the UniProt database for S. gordonii DL1 d) Theoretical values for S. gordonii DL1 proteins e) The sequenced peptides identified by LC-MS/MS can be found in supplemental material (Additional file 1) f) Protein identity deduced from adjacent identified spot g) Proteins identified by only one peptide are given when only a single match was yielded from the database search

Summary

Introduction

To respond and adapt to environmental challenges, prokaryotes regulate cellular processes rapidly and reversibly through protein phosphorylation and dephosphorylation. Intracellular proteins from planktonic cells of S. gordonii DL1 were extracted and subjected to 2D-gel electrophoresis. Phosphorylated proteins were visualized with ProQ Diamond Phosphoprotein Gel Stain. S. gordonii can passively migrate from small oral lesions through the blood stream and cause infective endocarditis by opportunistic infection of the heart valves [3]. This mainly saccharolytic species is considered a commensal with ubiquitous habitation in humans, and given the acid production and Robertsson et al BMC Microbiology (2020) 20:280 uptake as well as drain themselves of glycolytic intermediates by producing large amounts of lactic acid. The ATR is dependent on molecular chaperone activity [4, 8] that sustains correct protein folding during biosynthesis even at low pH

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