Comprehensive analysis of the lysine acetylome and its potential regulatory roles in the virulence of Streptococcus pneumoniae.

Unlabelled: Protein lysine acetylation is a well-known modification with vital regulatory roles in various biological processes. Currently, the acetylated proteome in Streptococcus pneumoniae (S. pneumoniae) is not yet clear. Combining immune-affinity enrichment with mass spectrometry-based proteomics, we identified the first lysine acetylome of S. pneumoniae. In total, 653 lysine acetylated sites on 392 proteins were identified, which are involved in diverse important biological pathways, including gene expression and central metabolism. S. pneumoniae has a relatively high acetylation level, implying its prominent and diverse roles in the regulation of biological processes. In the acetylome of S. pneumoniae, the most frequently occurring motifs of acetylation are KK, KR, KxK, KxxK and KH. Compared with the reported acetylation motifs in various bacterial species, the motif unique to S. pneumoniae is KT, indicating that species-specific characteristics, regulations and molecular mechanisms of acetylation may exist in this bacterium. Notably, many proteins directly or indirectly contributing to virulence are prevalently acetylated, suggesting that acetylation may coordinate bacterial virulence. This work presented here provides the first system-wide analysis of lysine acetylation in Streptococcus species, which may facilitate a deeper understanding on the regulatory roles of acetylation in the bacteria.

Biological Significance: S. pneumoniae causes a series of serious human diseases. Protein acetylation regulates many important biological pathways in bacteria. In this study, the first lysine acetylome of S. pneumoniae was identified and comprehensively analyzed with bioinformatics methods. One unique acetylated motif (KT) was identified, suggesting that specific characteristics of lysine acetylation reaction may exist in S. pneumoniae. Besides, our data suggest that lysine acetylation closely regulates bacterial virulence. Further study focusing on the biological functions of these acetylproteins may provide important clues for the therapy of S. pneumoniae infection.