Contribution of cysteine residue to the properties of Listeria monocytogenes listeriolysin O.
Listeriolysin (LLO) is the key virulence factor critical for Listeria monocytogenes pathogenesis. Listerial cytolysin belongs to the family of cholesterol-dependent cytolysins (CDCs), a group of pore-forming toxins produced by related gram-positive bacteria. Most CDCs contain a cysteine residue in the conserved undecapeptide - a sequence that is highly preserved among this group of proteins. Substitutions of cysteine do not always lead to loss of hemolytic activity, questioning the purpose of such strong conservation of this amino acid in the sequence of CDC. The properties of 3 L. monocytogenes strains, a wild type and 2 mutants expressing modified LLO within the cysteine residue, were analyzed in this work. The first of these mutants producing a toxin with cysteine to alanine substitution showed similar features to the wild type except that a thiol-reducing agent was not necessary for hemolytic activity. Another strain secreting LLO containing serine instead of cysteine exhibited strikingly different properties than the wild type. Modified toxin is independent of the reducing reagents, less stable, and shows accelerated kinetics of cytolysis in comparison with the unchanged protein. However, both mutant strains are less invasive in the cell culture model showing the important role of cysteine in L. monocytogenes virulence.
Stachowiak
Radosław
R
Department of Applied Microbiology, Institute of Microbiology, University of Warsaw, Miecznikowa 1, Warsaw 02-096, Poland. radeks@biol.uw.edu.pl
Wiśniewski
Jarosław
J
Osińska
Olga
O
Bielecki
Jacek
J
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D002417:Cattle; D002460:Cell Line; D003545:Cysteine / Q000737:chemistry; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D006461:Hemolysis / Q000187:drug effects; D066298:In Vitro Techniques; D008089:Listeria monocytogenes / Q000737:chemistry* / Q000235:genetics / Q000472:pathogenicity; D008958:Models, Molecular; D055550:Protein Stability; D051381:Rats; D012756:Sheep; D014774:Virulence
D001427:Bacterial Toxins; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D003545:Cysteine; C038705:hlyA protein, Listeria monocytogenes