W. Nagahama et al., Role of tryptophan-1 in hemolytic and phospholipase C activities of Clostridium perfringens alpha-toxin, MICROB IMMU, 44(7), 2000, pp. 585-589
Replacement of the Trp-1 in Clostridium perfringens alpha-toxin with tyrosi
ne caused no effect on hemolytic and phospholipase C (PLC) activities or on
binding to the zinc ion, but that of the residue with alanine, glycine and
histidine led to drastic decreases in these activities and a significant r
eduction in binding to the zinc ion. The hemolytic and PLC activities of W1
H and W1A were significantly increased by the preincubation of these varian
t toxins with zinc ions, but the preincubation of W1G with the metal ion ca
used little effect on these activities. Gly-Ile-alpha-toxin, which containe
d an additional Gly-Ile linked to the N-terminal amino acid of alpha-toxin,
did not show hemolytic activity; but showed about 6% PLC activity of the w
ild-type toxin. A mutant toxin, which contained an additional Gly-Ile linke
d to the N-terminus of a protein lacking 4 N-terminal residues of alpha-tox
in, showed about 1 and 6% hemolytic and PLC activities of the wild-type tox
in, respectively. Incubation of the mutant toxin with zinc ions caused a si
gnificant increase in PLC activity These observations suggested that Trp-1
is not essential for toxin activity, but plays a role in binding to zinc io
ns.