Ser170 of Bacillus thuringiensis Cry1Ab δ-endotoxin becomes anchored in a hydrophobic moiety upon insertion of this protein into Manduca sexta brush border membranes

Table 1 Toxicity assays and voltage clamping parameters

Toxin	^aLC₅₀ ng/cm²	^bSlope, μA/min	^cT₀ min.
Cry1Ab	36.00 (19.9-57.8)	-13.42 ± 0.70 -10.93 ± 0.27^d	4.00 ± 0.14 4.22 ± 0.12^d
L157C	78.60 (51.3-143.3)	-7.03 ± 0.22	7.58 ± 0.60
L157R₁	101.75 (95.65-107.85)	-4.27 ± 0.80	8.04 ± 0.20
S170C	40.24 (27.17-56.16)	-11.85 ± 0.60	3.93 ± 0.60
S170R₁	42.61 (31.76-56.31)	-10.73 ± 0.20	3.08 ± 0.60
S176C	62.15 (34.00-92.90)	-5.56 ± 0.10	6.84 ± 0.15
S176R₁	130.68 (125.06-136.75)	-3.39 ± 0.12	14.00 ± 0.10

^a: 50% Lethal doses concentration, numbers in parenthesis represent 95% confidence limits.
^b: Slope: was obtained by fitting the straight portion of the curve to a linear equation.
^c: T₀, defined as the insertion time. This was calculated with equation (1).
^d: Cry1Ab wild type toxin in the presence of MTS spin-label.

ISSN: 1471-2091