Journal
BIOCHEMICAL JOURNAL
Volume 419, Issue -, Pages 555-564Publisher
PORTLAND PRESS LTD
DOI: 10.1042/BJ20081351
Keywords
serine protease; serine protease-like; SplA; Staphylococcus aureus; substrate specificity
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Funding
- Polish Ministry of Science and Higher Education [13033, N N301 032834]
- European Social Fund and Polish National Budget
- Foundation for Polish Science
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Staphylococcus aureus is a dangerous human pathogen whose antibiotic resistance is steadily increasing and no efficient vaccine is as yet available. This serious threat drives extensive studies on staphylococcal physiology and pathogenicity pathways, especially virulence factors. Spl (serine protease-like) proteins encoded by an operon containing up to six genes are a good example of poorly characterized secreted proteins probably involved in virulence. In the present Study, we describe an efficient heterologous expression system for SplA and detailed biochemical and structural characterization of the recombinant SplA protease. The enzyme shares a significant sequence homology to V8 protease and epidermolytic toxins which are well documented staphylococcal virulence factors. SplA has a very narrow substrate specificity apparently imposed by the precise recognition of three amino acid residues positioned N-terminal to the hydrolysed peptide bond. To explain determinants of this extended specificity we resolve the crystal structure of SplA and define the consensus model of substrate binding. Furthermore we demonstrate that artificial N-terminal elongation of mature SplA mimicking a naturally present signal peptide abolishes enzymatic activity. The probable physiological role of the process is discussed. Of interest, even though precise N-terminal trimming is a common regulatory mechanism among SI family enzymes, the crystal structure of SplA reveals novel significantly different mechanistic details.
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