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Vesicular stabilization and activity augmentation of enterohaemorrhagic Escherichia coli haemolysin
Author(s) -
Aldick Thomas,
Bielaszewska Martina,
Uhlin Bernt Eric,
Humpf HansUlrich,
Wai Sun Nyunt,
Karch Helge
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06618.x
Subject(s) - biology , hemolysin , virulence , escherichia coli , haemolysis , virulence factor , microbiology and biotechnology , toxin , bacterial outer membrane , anthrax toxin , vesicle , biochemistry , membrane , gene , immunology , fusion protein , recombinant dna
Summary Haemolysin from enterohaemorrhagic Escherichia coli (EHEC‐Hly), a putative EHEC virulence factor, belongs to the RTX (repeat‐in‐toxin) family whose members rapidly inactivate themselves by self‐aggregation. By investigating the status of EHEC‐Hly secreted extracellularly, we found the toxin both in a free, soluble form and associated, with high tendency and independently of its acylation status, to outer membrane vesicles (OMVs) extruded by EHEC. We compared the interaction of both toxin forms with erythrocytes using scanning electron microscopy and binding assays. The OMV‐associated toxin was substantially (80 times) more stable under physiological conditions than the free EHEC‐Hly as demonstrated by prolonged haemolytic activity (half‐life time 20 h versus 15 min). The haemolysis was preceded by calcium‐dependent binding of OMVs carrying EHEC‐Hly to erythrocytes; this binding was mediated by EHEC‐Hly. We demonstrate that EHEC‐Hly is a biologically active cargo in OMVs with dual roles: a cell‐binding protein and a haemolysin. These paired functions produce a biologically potent form of the OMV‐associated RTX toxin and augment its potential towards target cells. Our findings provide a general concept for stabilization of RTX toxins and open new insights into the biology of these important virulence factors.