A. Podbielski et al., IMMUNOGLOBULIN-BINDING FCRA AND ENN PROTEINS AND M-PROTEINS OF GROUP-A STREPTOCOCCI EVOLVED INDEPENDENTLY FROM A COMMON ANCESTRAL PROTEIN, Medical microbiology and immunology, 183(1), 1994, pp. 33-42
Significant sequence homology between M proteins and immunoglobulin (I
g)-binding proteins of group A streptococci suggests that these protei
ns arose by gene duplication followed by the development of functional
diversity due to mutations and intragenic recombinations. The deduced
sequence of multiple Ig-binding proteins and M proteins were compared
to distinguish between two evolutionary models. Did these functionall
y distinct genes originate in the distant past from duplication of a c
ommon ancestral gene and then functionally evolve independently or did
they evolve more recently, one from the other by duplication of a fix
ed gene? Multiple alignments of conserved sequences of these proteins
are consistent with the former hypothesis. Comparison of N termini of
Ig-binding proteins revealed less diversity than that of the M protein
s' N termini, suggesting that these proteins are under less selective
pressure to change.