DIFFERENT ALLELES OF THE FCRA MRP GENE OF STREPTOCOCCUS-PYOGENES ENCODE M-RELATED PROTEINS EXHIBITING AN IDENTICAL IMMUNOGLOBULIN-BINDING PATTERN/

The majority of group A streptococci (GAS, Streptococcus pyogenes) exp ress immunoglobulin (Ig)-binding proteins. The genes encoding these pr oteins belong either to the emm or the emm-related (fcrA/mrp and enn) gene family and are located in close proximity on the GAS genome, wher e they form part of the vir regulon. In the present study analysis of sequence data of the 5' terminal portions of the fcrA/mrp genes from G AS isolates representing 37 different M serotypes led to a classificat ion of six different types. Thus, although fcrA/mrp genes exhibit an a llelic polymorphism, they do not display the high degree of N-terminal sequence diversity found among emm genes. The nucleotide sequences of the fcrA/mrp genes from 3 GAS isolates, belonging to serotypes M8, M9 , and M13 and representing newly characterized fcrA/mrp gene types, ar e reported. Analysis of the Ig-binding properties of recombinant FcrA/ Mrp8, 9, and 13 proteins, demonstrated a similar Ig-binding profile be ing reactive with human IgG subclasses 1, 2, and 4. This pattern is id entical to that previously described for other recombinant fcrA/mrp4, 49, 64/14 and 76 gene products, indicating that this property is not a ffected by the N-terminal variability. Evidence for recombination betw een an fcrA/mrp and an mga gene was observed in an M-type 33 strain is olate providing further support for the concept of gene rearrangement contributing to the diversity of vir regulon gene products.