Fig. 4.

SIP-contacting residues in RopB are crucial for speB expression. a RopB–SIP-binding constants for recombinant RopB mutant proteins containing single alanine replacements in SIP-contacting amino acid residues. Characterization of isogenic ropB mutant strains for (b) speB gene transcript levels, (c) immunoreactive secreted SpeB levels, and (d) SpeB protease activity. P values (****P < 0.0001) of the indicated strains were compared to ∆ropB mutant strain. P values were determined by t test. Source data are provided as a Source Data file. e Twenty outbred CD-1 mice per strain were injected intramuscularly with 1 × 10⁷ CFUs of each indicated strain. Kaplan–Meier survival curve with P values derived by log rank-test are shown. f Histopathology scores of hindlimb lesions from mice infected with each indicated strain. Histopathology analysis of the infected hindlimbs was performed at 48 h post-inoculation. Data are expressed as means + standard deviation. P values (*P < 0.05) of the indicated strains were compared to isogenic ∆ropB mutant strain. P values were determined by t test. g Analysis of the speB transcript level in the intramuscular lesions from mice infected with indicated strains. Samples were collected 24 h postinoculation from the lesions (n = 5 per strain) and analyzed in triplicate by qRT-PCR. The speB transcript levels in wild-type GAS grown in THY to late-exponential growth phase (WT-LE, A₆₀₀ ~1.5) was used as a reference and fold-changes in speB transcript levels relative to the reference are shown. P values were determined by t test