Release of protein A from the cell wall of Staphylococcus aureus

Significance Surface proteins are linked to the cell wall of Gram-positive bacterial pathogens by a mechanism requiring LPXTG motif sorting signals and sortase. Here we show that surface proteins are also released from the bacterial surface into the extracellular milieu and may fulfill functions similar to secreted polypeptides. We demonstrate that protein A of Staphylococcus aureus , a B cell superantigen, is released with peptidoglycan linked to its C terminus. Release of protein A involves murein hydrolases that remove immunostimulatory N -acetylmuramic acid and GlcNAc residues and liberate the polypeptide from the envelope. This mechanism of surface protein release may be universal for surface proteins of Gram-positive bacteria.