SepA, the 110 kDa protein secreted by Shigella flexneri: two-domain structure and proteolytic activity.
Shigellosis is characterized by a strong inflammatory response which is induced by bacteria invading the colonic mucosa. Characterization of a sepA mutant indicated that SepA, the major protein secreted by Shigella flexneri growing in laboratory media, might be involved in invasion and destruction of the host intestinal epithelium. The sequence of the first 500 residues of mature SepA (110 kDa) is homologous to that of the N-terminal region of IgA1 proteases. To investigate the potential proteolytic activity of SepA, the activity of the purified protein on a wide range of synthetic peptides was tested. SepA hydrolysed several of these substrates and the activity was inhibited by PMSF. Several peptides which were hydrolysed by SepA have been described as specific substrates for cathepsin G, a serine protease produced by polymorphonuclear leukocytes that was proposed to play a role in inflammation. However, unlike cathepsin G, SepA degraded neither fibronectin nor angiotensin I and had no effect on aggregation of human platelets. In addition, analysis of SepA hydrolysis by proteinase K suggested that the protein is composed of two domains of about 450 residues separated by a hinge region of 100 residues. The 47 kDa N-terminal domain was stable and endowed with proteolytic activity.
Unit� de Pathog�nie Microbienne Mol�culaire, INSERM U389, Institut Pasteur28 rue du Docteur Roux, 75724 Paris Cedex 15France.
Zineb
Z
Benjelloun-Touimi
Unit� de Pharmacologie Cellulaire, Institut Pasteur25 rue du Docteur Roux, 75724 Paris Cedex 15France.
Mustapha
M
Si Tahar
Centro CNR Biomembrane and Dipartimento di Scienze Biomediche, Universita di PadovaVia Trieste 75, 35121 PadovaItaly.
Cesare
C
Montecucco
Unit� de Pathog�nie Microbienne Mol�culaire, INSERM U389, Institut Pasteur28 rue du Docteur Roux, 75724 Paris Cedex 15France.
Philippe J
PJ
Sansonetti
Unit� de Pathog�nie Microbienne Mol�culaire, INSERM U389, Institut Pasteur28 rue du Docteur Roux, 75724 Paris Cedex 15France.
Claude
C
Parsot
D000803:Angiotensin I / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology*; D056649:Cathepsin G; D002403:Cathepsins / Q000378:metabolism; D002853:Chromatography, Liquid; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K / Q000494:pharmacology; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D009154:Mutation; D011480:Protease Inhibitors / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism; D012763:Shigella flexneri / Q000201:enzymology* / Q000235:genetics; D014105:Tosyl Compounds / Q000494:pharmacology
D001426:Bacterial Proteins; D005353:Fibronectins; D011480:Protease Inhibitors; C096725:SepA protein, Shigella; D014105:Tosyl Compounds; C003614:4-toluenesulfonyl fluoride; D000803:Angiotensin I; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D019286:Endopeptidase K