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Infect. Immun., May 1997, 1830-1835, Vol 65, No. 5
S Miyoshi, K Sasahara, S Akamatsu, MM Rahman, T Katsu, K Tomochika and S Shinoda
Vibrio mimicus is a causative agent of human gastroenteritis. This pathogen
secretes a pore-forming toxin, V. mimicus hemolysin (VMH), which causes
hemolysis by three sequential steps: binding to an erythrocyte membrane,
formation of a transmembrane pore, and disruption of the cell membrane. VMH
with a molecular mass of 63 kDa was purified by ammonium sulfate
precipitation and column chromatography with phenyl Sepharose HP and
Superose 6 HR. The hemolytic reaction induced by VMH continued up to
disruption of all erythrocytes in the assay system. Moreover, VMH that
bound preliminarily to erythrocyte ghosts showed a sufficient ability to
attack intact erythrocytes. These results suggest reversible binding of the
toxin molecule to the membrane. The final cell-disrupting stage was
effectively inhibited by various divalent cations. Additionally, some
cations, such as Zn2+ and Cu2+, blocked the pore-forming stage at high
concentrations. Although VMH could disrupt all kinds of mammalian
erythrocytes tested, those from horses were most sensitive to the
hemolysin. Horse erythrocytes were found to have the most toxin-binding
sites and to be hemolyzed by the least amount of membrane-bound toxin
molecules, suggesting that toxin binding to and pore formation on
erythrocytes are more effective in horses than in other mammals. Purified
VMH induced fluid accumulation in a ligated rabbit ileal loop in a
dose-dependent manner. In addition, the antibody against the hemolysin
obviously reduced enteropathogenicity of living V. mimicus cells. These
findings clearly demonstrate that VMH is probably involved in the virulence
of this human pathogen.
Copyright © 1997, American Society for Microbiology
Purification and characterization of a hemolysin produced by Vibrio mimicus
Faculty of Pharmaceutical Sciences, Okayama University, Tsushima-Naka, Japan. miyoshi@pheasant.pharm.okayama-u.ac.jp
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