Infection and Immunity, August 2001, p. 4742-4748, Vol. 69, No. 8
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.8.4742-4748.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Microbiology and Tumorbiology Center, Karolinska Institutet, S-17177 Stockholm, Sweden
Received 5 February 2001/Returned for modification 14 March 2001/Accepted 16 May 2001
Data have been presented indicating that Staphylococcus
aureus cell surface protein can be degraded by extracellular
proteases produced by the same bacterium. We have found that in
sarA mutant cells, which produce high amounts of four major
extracellular proteases (staphylococcal serine protease [V8 protease]
[SspA], cysteine protease [SspB], aureolysin [metalloprotease]
[Aur], and staphopain [Scp]), the levels of cell-bound
fibronectin-binding proteins (FnBPs) and protein A were very low
compared to those of wild-type cells, in spite of unaltered or
increased transcription of the corresponding genes. Cultivation of
sarA mutant cells in the presence of the global protease
inhibitor
2-macroglobulin resulted in a 16-fold increase
in cell-bound FnBPs, indicating that extracellular proteases were
responsible for the decreased amounts of FnBPs in sarA
mutant cells. The protease inhibitor E64 had no effect on the level of
FnBPs, indicating that cysteine proteases were not involved.
Inactivation of either ssp or aur in the
prototype S. aureus strain 8325-4 resulted in a threefold increase in the amount of cell-bound FnBPs. Inactivation of the same
protease genes in a sarA mutant of 8325-4 resulted in a 10- to 20-fold increase in cell-bound protein A. As the serine protease requires aureolysin to be activated, it can thus be concluded that the
serine protease is the most important protease in the release of
cell-bound FnBPs and protein A.
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