Table 2 - Protein engineering of d-endotoxins of Bacillus thuringiensis

Table 2. Domain-I mutations related to ion channel formation /conductance.

S.no	Toxin	Residue(s)	Mutation(s)	Effect	Reference
1.	Cry1Ab	50	F-K	Loss of toxicity due to impaired pore formation	Ahmed and Ellar, 1990
2.	Cry1Ac	'N' terminal fragment of toxin	-	Forms ion channel in PLB	Walters et al. 1993
3.	Cry3B2	Domain I alone	-	Forms ion channel on PLB but less than that of native toxin	Von Tersch et al. 1994
4.	Cry1Ac	92	A-D	Except Negatively charged substitutions all changes of Ala-92 were fully toxic	Wu and Aronson, 1992
	Cry1Ac	93	R-H R-G R-A R-S	3-10 folds reduction in toxicity due to loss of positive charge.	Wu and Aronson, 1992
5.	Cry1Ac	206-215	R209A, P T213A W210L V218N Y211N, R, D	No change in toxicity	Aronson et al. 1995
6.	Cry1Ac	a Helix-7	Substituted with Diphtheria Toxin Fragment	Enhanced toxicity due to larger pore formation	Chandra et al. 1999
7.	Cry1Ac	Helix 7 amino acids 210 211 211 214	W-C Y-D Y-C G-E	No alteration in toxicity on tested insects	Aronson et al. 1995
8.	Cry1Aa	-	Disulphide bridging of Domain I region	Reduced ion channel conductance in oxidized condition	Schwartz et al. 1997
9.	Cry1Aa	521	R-K R-Q R-H R-E R-K	Reverse the ion conductance Reverse the ion conductance No change in conductance No change in conductance No change in conductance	Schwartz et al. 1997
10.	Cry1Aa	526 532	R-K R-K	Specifically reduces the toxin's inhibition of I_SC	Chen et al. 1993
11.	Cry1Ac1	135	N-Q	Binding to BBMV membrane not affected, pore formation affected	Tigue et al. 2001
12.	Cry1Ac	132 130 131	I-S, L, V, N M-T M-I	Reduced the toxicity No change in toxicity No change in toxicity	Manoj Kumar and Aronson, 1999