The M protein is dispensable for maturation of streptococcal cysteine protease SpeB.
The streptococcal pyrogenic exotoxin B (SpeB) is an important virulence factor of group A streptococci (GAS) with cysteine protease activity. Maturation of SpeB to a proteolytically active form was suggested to be dependent on cell-wall-anchored M1 protein, the major surface protein of GAS (M. Collin and A. Olsen, Mol. Microbiol. 36:1306-1318, 2000). Collin and Olsen showed that mutant GAS strains expressing truncated M protein secrete a conformationally different form of unprocessed SpeB with no proteolytic activity. Alternatively, we hypothesized that a truncated M protein may interfere with processing of this secreted protease, and therefore we tested cysteine protease activity in genetically defined mutant strains that express either no M protein or membrane-anchored M protein with an in-frame deletion of the AB repeat region. Measurements of SpeB activity by cleavage of a substrate n-benzoyl-Pro-Phe-Arg-p-nitroanilide hydrochloride showed that the proteolytic activities in culture supernatants of both mutants were similar to those from the wild-type strain. In addition, Western blot analysis of culture supernatants showed that SpeB expression and processing to a mature form was unaffected by either deletion mutation. Therefore, we conclude that M protein is not required for maturation of the streptococcal cysteine protease SpeB.
Zimmerlein
Björn
B
Department of Microbiology, University of Minnesota Medical School, 1460 Mayo Bldg., MMC196, 420 Delaware Street SE, Minneapolis, MN 55455, USA.
Park
Hae-Sun
HS
Li
Shaoying
S
Podbielski
Andreas
A
Cleary
P Patrick
PP
D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018929:Cell Culture Techniques; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D005098:Exotoxins / Q000378:metabolism*; D009154:Mutation; D013297:Streptococcus pyogenes / Q000235:genetics / Q000378:metabolism*
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D005098:Exotoxins; C027951:erythrogenic toxin; C014689:streptococcal M protein; D003546:Cysteine Endopeptidases