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Fig. 5 | BMC Microbiology

Fig. 5

From: Identification of the minimal cytolytic unit for streptolysin S and an expansion of the toxin family

Fig. 5

Hemolytic activity of SLS-like peptides expressed in S. pyogenes ΔsagA and modified by purified SagBCD enzymes. a Residues of the SagA and SagA-BvalA precursors are numbered. The motifs known to be important for binding SagC [7] are shown in red for the SagA leader. Partial binding motifs are also shown in red for the BvalA leader. Potentially modified residues are blue except C32, the position of a previously generated alanine substitution that abolished cytolytic activity of SagA, which is marked in purple. The predicted leader cleavage sites are indicated with a caret. The minimal core region required for hemolytic activity of SLS in S. pyogenes ΔsagA(SagA24–34) is underlined. The position of a stop codon introduced in SagA to yield the SagA1–35 (BvalA mimic) is marked with an asterisk. SagA-BvalA-S27C and SagA-BvalA + A point mutants are represented by italicized letters adjacent to the SagA-BvalA precursor sequence. The precursor peptide labels continue in panel B & C. b A representative colony on blood agar of S. pyogenes ΔsagA expressing each precursor peptide from pDCerm is shown. The colony labeled “Empty” was a negative control containing pDCerm vector. c Where appropriate, bars are labeled with + or – indicating presence or absence, respectively, of MBP-SagBCD in the reaction using the indicated MBP-tagged precursor peptide. Triton X-100, positive control for 100 % lysis; PBS, negative control for background hemolysis. Error is reported as the standard deviation of the mean (n = 3). * indicates P < 0.01 for each synthetase reaction versus the relevant unreacted precursor. P < 0.01 for all lytic samples versus all negative controls, i.e. SagA-C32A reaction, enzymes alone (labeled SagB, SagC, SagD, and SagBCD), PBS

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