Mdp. Boyle et al., ANALYSIS OF GENES ENCODING 2 UNIQUE TYPE IIA IMMUNOGLOBULIN G-BINDINGPROTEINS EXPRESSED BY A SINGLE GROUP-A STREPTOCOCCAL ISOLATE, Infection and immunity, 62(4), 1994, pp. 1336-1347
An emm-like gene (emmL) and a fcrA gene from group A streptococcal str
ain 64/14 (emmL(64/14) and fcrA(64/14)) were amplified by PCR and forc
e cloned into the heat-inducible expression vector pJLA 602. The emml
gene encoded a recombinant protein that bound human IgG1, IgG2, and Ig
G4 in a nonimmune fashion. This is the reactivity profile of a type II
a IgG-binding protein. The emmL(64/14) gene product was antigenically
similar to the previously identified high-molecular-weight type IIa Ig
G-binding protein of strain-64/14 and had an N-terminal sequence ident
ical to that of the wild-type protein. The fcrA gene also encoded a re
combinant protein with type IIa functional activity. This protein was
similar to the lower-molecular-weight type IIa IgG-binding protein pre
viously isolated from strain 64/14 and was antigenically distinct from
the higher-molecular-weight type IIa protein encoded by the emmL(64/1
4) gene. The sequences for both genes including: the intervening regio
ns are presented. The emmL gene demonstrates significant homology to o
ther class I emm and emmL genes expressed by opacity factor-negative g
roup A streptococcal isolates. The fcr A gene was found to be homologo
us to other fcrA genes normally present in opacity factor-positive gro
up A isolates. The sequence upstream of the fcrA gene and the interven
ing sequence between the end of the fcrA gene and the start of the emm
L gene were similar to those reported for other fcrA genes.