Haemolysin of Escherichia coli: comparison of pore-forming properties between chromosome and plasmid-encoded haemolysins.
Lipid bilayer experiments were performed with chromosome-encoded haemolysin of Escherichia coli. The addition of the toxin to the aqueous phase bathing lipid bilayer membranes of asolectin resulted in the formation of transient ion-permeable channels with two states at small transmembrane voltages. One is a prestate (single-channel conductance 40 pS in 0.15 M KCl) of the open state, which had a single-channel conductance of 420 pS in 0.15 M KCl and a mean lifetime of 30 s. Membranes formed of pure lipids were rather inactive targets for this haemolysin. Experiments with different salts suggested that the haemolysin channel was highly cation-selective at neutral pH. The mobility sequence of the cations in the channel was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with a wide, water-filled channel with an estimated minimal diameter of about 1 nm. The pore-forming properties of chromosome-encoded haemolysin were compared with those of plasmid-encoded haemolysin. Both toxins share common features, oligomerize probably to form pores in lipid bilayer membranes. Both types of haemolysin channels have similar properties but different lifetimes.
Benz
R
R
Lehrstuhl für Biotechnologie, Universität Würzburg, FRG.
Döbereiner
A
A
Ludwig
A
A
Goebel
W
W
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000633:toxicity*; D002876:Chromosomes, Bacterial; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000633:toxicity*; D007473:Ion Channels / Q000187:drug effects*; D008969:Molecular Sequence Data; D010957:Plasmids
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D007473:Ion Channels