Quantitative acetylome analysis reveals involvement of glucosyltransferase acetylation in Streptococcus mutans biofilm formation.

Streptococcus mutans (S. mutans) effectively utilizes dietary sucrose for the exopolysaccharide productions, which are mostly synthesized by the effects of glucosyltransferases (Gtfs). In the present study, the acetylome of S. mutans was identified and quantitative acetylome analysis of the bacterial biofilm growth (SMB) was compared with that of planktonic growth (SMP). The dynamic changes of protein acetylation were quantified using the integrated approach involving TMT labeling and Kac affinity enrichment followed by high-resolution mass spectrometry-based quantitative proteomics. In total, 973 acetylation sites in 445 proteins were identified, among which 617 acetylation sites in 302 proteins were quantitated. The overall analysis indicated that 22.7% of proteins were acetylated. Among the quantified proteins in SMB, the acetylation degree of lysine in 56 sites increased, while that of lysine decreased in 52 sites. In the acetylome of S. mutans, six significantly enriched motifs were identified and obtained including Kac****K, KacF, Kac****R, KacY, KacH, F*Kac. In addition, KEGG pathway-based enrichment analysis indicated significant enrichments in glycolysis/gluconeogenesis, and RNA degradation. Particularly, most downregulated acetylated lysine proteins were glucosyltransferase-SI, glucosyltransferase-I, and glucosyltransferase-S in S. mutans biofilm, which probably reveals a switch-off mechanism for the regulation of glucosyltransferases function during the biofilm development.