Publication: Effects on larvicidal activity of single proline substitutions in α3 or α4 of the bacillus thuringiensis CRY4B toxin
Issued Date
1998-01-01
Resource Type
ISSN
10399712
Other identifier(s)
2-s2.0-0031923098
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Mahidol University
Rights Holder(s)
SCOPUS
Bibliographic Citation
Biochemistry and Molecular Biology International. Vol.44, No.4 (1998), 825-832
Suggested Citation
Panapat Uawithya, Tipparat Tuntitippawan, Gerd Katzenmeier, Sakol Panyim, Chanan Angsuthanasombat Effects on larvicidal activity of single proline substitutions in α3 or α4 of the bacillus thuringiensis CRY4B toxin. Biochemistry and Molecular Biology International. Vol.44, No.4 (1998), 825-832. Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/18318
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Title
Effects on larvicidal activity of single proline substitutions in α3 or α4 of the bacillus thuringiensis CRY4B toxin
Abstract
The possible role of α-helices 3 and 4 in toxicity of the dipteran-active Bacillus thuringiensis Cry4B δ-endotoxin was investigated by employing proline substitutions via site-directed mutagenesis. Similar to the wild-type Cry4B, the mutant toxins were over-expressed in Escherichia coli as cytoplasmic inclusions and were structurally stable upon solubilization and trypsin activation. The substitution of glutamine 149 by proline in the center of helix 4 (Q149P) resulted in a nearly complete loss of toxicity against Aedes aegypti mosquito-larvae. However, single proline replacements near the center of helix 3 (V1 19P) and at the N-terminus of helix 4 (Q140P) did not decrease larvicidal activity. The toxicity of E. coli cells expressing the wild-type toxin was significantly reduced by two-hour preincubation with the non-toxic mutant (Q149P), thus indicating that the primary binding step was not affected by the proline substitution in helix 4. The results therefore reveal a crucial role for helix 4 of the Cry4B toxin in toxicity, possibly in membrane insertion and pore formation rather than in receptor recognition.