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Open AccessArticle

Channel Formation by LktA of Mannheimia (Pasteurella) haemolytica in Lipid Bilayer Membranes and Comparison of Channel Properties with Other RTX-Cytolysins

1
Department of Life Sciences and Chemistry, Jacobs-University Bremen gGmbH Campusring, 1; 28759 Bremen, Germany
2
Vaccine and Infectious Disease Organization-International Vaccine Centre, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N5E3, Canada
*
Author to whom correspondence should be addressed.
Toxins 2019, 11(10), 604; https://doi.org/10.3390/toxins11100604
Received: 26 August 2019 / Revised: 22 September 2019 / Accepted: 10 October 2019 / Published: 17 October 2019
(This article belongs to the Special Issue RTX Toxins)
Cytolysin LktA is one of the major pathogenicity factors of Mannheimia haemolytica (formerly Pasteurella haemolytica) that is the cause of pasteurellosis, also known as shipping fever pneumonia, causing substantial loss of sheep and cattle during transport. LktA belongs to the family of RTX-toxins (Repeats in ToXins) that are produced as pathogenicity factors by a variety of Gram-negative bacteria. Sublytic concentrations of LktA cause inflammatory responses of ovine leukocytes. Higher concentrations result in formation of transmembrane channels in target cells that may cause cell lysis and apoptosis. In this study we investigated channel formation by LktA in artificial lipid bilayer membranes made of different lipids. LktA purified from culture supernatants by polyethylene glycol 4000 precipitation and lyophilization had to be activated to frequently form channels by solution in 6 M urea. The LktA channels had a single-channel conductance of about 60 pS in 0.1 M KCl, which is about one tenth of the conductance of most RTX-toxins with the exception of adenylate cyclase toxin of Bordetella pertussis. The LktA channels are highly cation-selective caused by negative net charges. The theoretical treatment of the conductance of LktA as a function of the bulk aqueous concentration allowed a rough estimate of the channel diameter, which is around 1.5 nm. The size of the LktA channel is discussed with respect to channels formed by other RTX-toxins. We present here the first investigation of LktA in a reconstituted system. View Full-Text
Keywords: RTX-toxin; cytolysin; channel formation; shipping fever pneumonia; Mannheimia haemolytica; lipid bilayer membrane RTX-toxin; cytolysin; channel formation; shipping fever pneumonia; Mannheimia haemolytica; lipid bilayer membrane
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Benz, R.; Piselli, C.; Potter, A.A. Channel Formation by LktA of Mannheimia (Pasteurella) haemolytica in Lipid Bilayer Membranes and Comparison of Channel Properties with Other RTX-Cytolysins. Toxins 2019, 11, 604.

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