title: Architecture of the vir regulons of group A streptococci parallels opacity factor phenotype and M protein class.
abstract: Group A streptococci have traditionally been categorized into two broad groups based on the presence or absence of serum opacity factor (OF). Recent studies show that these two groups vary in a number of properties in addition to the OF phenotype, including sequence variations in the constant region of the antiphagocytic M protein genes, the presence or absence of immunoglobulin G Fc receptor proteins, and the presence or absence of multiple M protein-like genes situated in a tandem array. The M protein genes (emm) in OF- streptococcal strains are known to be part of a regulon of virulence-related genes controlled by the trans-acting positive regulatory gene, virR, situated just upstream of emm. In OF+ strains, however, the region adjacent to virR is occupied by an M protein-related, type IIa immunoglobulin G Fc receptor gene (fcrA), and the relative position of emm has not been determined. To further define the vir regulon in OF+ streptococci, we used the polymerase chain reaction to show that fcrA49 is situated immediately upstream of emm49 in the OF+ type 49 strain CS101. This result shows for the first time the separate identity and genetic linkage of these two genes in the vir regulon of an OF+ group A streptococcal strain and confirms our previous hypothesis that emm49 exists as the central gene in a trio of emm-like genes. Additionally, using DNA hybridizations, we found considerable sequence divergence between OF- and OF+ group A streptococci in virR and in the noncoding sequences between virR and the emm or fcrA expression site. We found, however, a high degree of sequence conservation in this region within each of the two groups of strains.
authors.affiliation: Department of Microbiology, University of Minnesota, Minneapolis 55455-0312.
authors.forename: E J
authors.initials: EJ
authors.lastname: Haanes
authors.forename: D G
authors.initials: DG
authors.lastname: Heath
authors.forename: P P
authors.initials: PP
authors.lastname: Cleary
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial; D000943:Antigens, Differentiation / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000235:genetics*; D010641:Phenotype; D011961:Receptors, Fc / Q000235:genetics; D017452:Receptors, IgG; D013297:Streptococcus pyogenes / Q000235:genetics*; D037521:Virulence Factors
chemical_list: D000942:Antigens, Bacterial; D000943:Antigens, Differentiation; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D011961:Receptors, Fc; D017452:Receptors, IgG; D037521:Virulence Factors; C021908:opacity factor; C014689:streptococcal M protein; D010447:Peptide Hydrolases