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. 2008 Nov 14;75(2):359–365. doi: 10.1128/AEM.01930-08

TABLE 1.

Summary of results

Toxin Chymotrypsin digestiona CD spectrumb Effect of DTT on toxin activity
Competitione
SDS-PAGEc Pore formationd
Cry1Aa Partial Wild type NAf
L126C mutant NDg ND ND
R127C mutant ND ND ++ ND
E128C mutant ND ND ++ + ND
E129C mutant Minor Wild type Trace Complete
M130C mutant ND ND ++ ND
R131C mutant Minor Wild type Trace Strong
I132C mutant Partial Lower + Strong
Q133C mutant ND ND ++ ND
F134C mutant ND ND + ND
N135C mutant Minor Wild type Trace Complete
M137C mutant ND ND ++ ND
N138C mutant Minor Wild type Strong
S139C mutant Minor Lower ++ + Strong
A140C mutant Partial Wild type Trace ND
L141C mutant ND ND + ND
T142C mutant Minor Wild type + Strong
A144C mutant Partial Wild type Strong
I145C mutant ND ND Trace + ND
P146C mutant ND ND Trace + ND
L147C mutant Minor Wild type Trace None
A149C mutant ND ND ND
V150C mutant Minor Lower + Strong
a

Apparent amounts indicate minor or partial digestion of the toxin to a fragment of about 55 kDa.

b

Compared with the Cry1Aa spectrum. “Wild type”, the spectrum of the mutant was similar to that of Cry1Aa; “Lower,” the α-helix content of the protein was decreased.

c

The presence of bands corresponding to a 120-kDa protein, characteristic of homodimers, was revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the absence of dithiothreitol (DTT) in amounts that were substantial (++), moderate (+), or trace. The absence of homodimer bands is indicated by a minus.

d

The presence of disulfide bridges as revealed by the effect of dithiothreitol on pore formation. The addition of dithiothreitol had either no effect (−) or produced increased (+) toxin activity.

e

Ability of each mutant to inhibit the formation of pores by Cry1Aa.

f

NA, not applicable.

g

ND, not determined.