CHARACTERIZATION OF A GENE CODING FOR A TYPE IIO BACTERIAL IGG-BINDING PROTEIN

Two antigenic classes of non-immune IgG-binding proteins can be expres sed by group A streptococci. One antigenic group of proteins is recogn ized by an antibody prepared against the product of a cloned fcr A gen e (anti-FcRA). In this study, the immunogen used to prepare the antibo dy that defines the second antigenic class was shown to be the product of the emm-like (emmL) gene of M serotype 55 group A isolate, A928. T he emmL55 gene expressed in E. coil produced an M(r) similar to 58,000 molecule which bound human IgG(1), IgG(2), IgG(3), and IgG(4), as wel l as horse, rabbit and pig Ige in a non-immune fashion. These properti es are characteristic of the previously described type IIo IgG-binding protein isolated from this strain. In addition, the recombinant prote in was reactive with human serum albumin and fibrinogen. The emmL 55 g ene sequence was analysed and found to have the organization and seque nce characteristics of a typical class I emm-like gene.