TABLE 1.

Channel-forming properties of wild-type and mutant VacA proteins

Protein	Time to −100 pA at −50 mV (min)a	Selectivityb	Ratio of avg currents (+50 mV/−50 mV)c	Ratio of channel formation rates (+50 mV/−50 mV)c
Wild type	33 ± 12 (9)	7.3 ± 1.4 (14)	1.3 ± 0.1 (16)	0.76 ± 0.33 (20)
V21L mutant	>160d (4)	NDe	ND	ND
V25L mutant	>615d (4)	ND	ND	ND
G121R mutant	29 ± 13 (5)	6.8 ± 0.8 (6)	1.3 ± 0.1 (14)	4.7 ± 1.9 (18)
S246L mutant	38 ± 14 (6)	6.9 ± 0.7 (6)	1.3 ± 0.1 (13)	2.8 ± 1.2 (18)

^aVacA preparations(30 nM, ∼2.7 μg/ml) were added to planar lipid bilayers in a buffer containing 5 mM citric acid, 100 mM sodium chloride, and 2 mM EDTA (pH 4). The time required to produce a current of 100 pA at −50 mV was then determined. Results represent the mean ± standard deviation from multiple independent determinations for each sample tested. The number of successfully completed experiments for each sample is in parentheses.

^bIon selectivity ratios (P_Cl/P_Na) are shown. Reversal potential was measured in cis (200 mM NaCl) and in trans (100 mM NaCl) with VacA samples at 30 nM. The number of experiments is in parentheses. Results represent means ± standard deviations.

^cThe number of measurements obtained from three separate experiments is in parentheses.

^dAfter prolonged incubation with these toxins, the membrane frequently ruptured before any stable current was observed. The average time at which the membrane ruptured is indicated.

^eND, not determined.