Characterization of a mazEF toxin-antitoxin homologue from Staphylococcus equorum

ABSTRACT

Toxin-Antitoxin (TA) systems encoded in prokaryotic genomes fall into five types, typically composed of two distinct small molecules, an endotoxic protein and a cis encoded antitoxin of ribonucleic or proteinaceous nature. In silico analysis revealed seven putative type I and three putative type II TA systems in the genome of the non-pathogenic species strain Staphylococcus equorum SE3. Among these, a MazEF system orthologue termed MazEF_seq, was further characterized. 5’ RACE revealed the expression and the transcriptional start site of mazE_seq, indicating an immediately upstream promoter. Heterologous expression of the putative toxin encoding mazF_seq gene imposed growth cessation but not cell death on E. coli. In vivo and in vitro, MazF_seq was shown to cleave at UACAU motifs which are remarkably abundant in a number of putative metabolic and regulatory S. equorum genes’ transcripts. Specific interaction between MazF_seq and the putative cognate antitoxin MazE_seq was demonstrated by bacterial two-hybrid analyses. These data strongly suggest that MazEF_seq represents the first characterized TA system in a non-pathogenic Staphylococcus species and indicates that MazEF modules in staphylococci may also control processes beyond pathogenicity.