FIG. 5.

Identification of a Rib-like protein expressed by type V strain 2471. (A) Inhibition test with whole bacteria. Suspensions of whole bacteria were used to inhibit the binding of rabbit anti-Rib antibodies to Rib immobilized in microtiter plates. Strains used were the Rib-expressing type III strain BM110, the type V strain 2471, and the type Ib strain SB35, which expresses the α and β proteins. (B) Western blot analysis of purified preparations of five GBS surface proteins: the α, β, Rib, Fbs, and Rib-like proteins. The blot was analyzed with mouse antiserum (diluted 1:500) against the purified Rib-like protein, and bound antibodies were detected with radiolabeled protein A. In a control blot with preimmune mouse serum, no signals were obtained. Molecular mass markers are in kilodaltons. (C) The N-terminal amino acid sequence of the Rib-like protein is identical to that of the α protein (26, 30). Experiments for panels A and B were performed twice with similar results.