B. Krebs et al., DIFFERENT ALLELES OF THE FCRA MRP GENE OF STREPTOCOCCUS-PYOGENES ENCODE M-RELATED PROTEINS EXHIBITING AN IDENTICAL IMMUNOGLOBULIN-BINDING PATTERN/, Medical microbiology and immunology, 185(1), 1996, pp. 39-47
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.