Regulation of host cell recognition in Streptococcus pyogenes.

Protein F, a fibronectin-binding protein, and the M protein of Streptococcus pyogenes both play important roles in directing adherence to different populations of host cells in the skin. Expression of both proteins is regulated in response to alterations in atmosphere. Transcriptional control of mry, a positive-acting regulator of expression of the gene which encodes the M protein (emm) in response, to elevated levels of CO2, is a mechanism for control of emm expression in response to atmosphere. Expression of protein F is controlled at the level of transcription in response to the concentration of O2, and its expression is stimulated in the presence of superoxide. Further support for a role of superoxide in regulation of prtF expression comes from the observation that an S. pyogenes mutant which contains an insertionally inactivated gene for superoxide dismutase (sod) becomes hypersensitive to superoxide and will express prtF constitutively. A second strain also demonstrates constitutive expression of prtF but contains a functional sod. Complementation analyses in this strain using a prtF allele cloned from a regulating host and a novel method for shuttle mutagenesis which utilized the transposon mini-gamma delta have been used to identify rofA, a positive-acting regulator of prtF expression. A model for the role of the surface proteins, F and M and their regulatory genes mry and rofA in streptococcal infections of the skin will be discussed.