Publication: Mutation of the hydrophobic residue on helix α5 of the Bacillus thuringiensis Cry4B affects structural stability
Issued Date
2003-08-15
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ISSN
09298665
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2-s2.0-0041703058
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Mahidol University
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SCOPUS
Bibliographic Citation
Protein and Peptide Letters. Vol.10, No.4 (2003), 361-368
Suggested Citation
Chartchai Krittanai, Apichai Bourchookarn, Wanwarang Pathaichindachote, Sakol Panyim Mutation of the hydrophobic residue on helix α5 of the Bacillus thuringiensis Cry4B affects structural stability. Protein and Peptide Letters. Vol.10, No.4 (2003), 361-368. doi:10.2174/0929866033478834 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/20700
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Title
Mutation of the hydrophobic residue on helix α5 of the Bacillus thuringiensis Cry4B affects structural stability
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Abstract
Cry4B toxin is a mosquito-larvicidal protein from the Bacillus thuringiensis subsp. israelensis. We have investigated the role of two conserved hydrophobic residues of Cry4B in structural stabilization. Substitutions of the leucine-175 and isoleucine-189 on helix α5 with valine and leucine did not affect the expression level, solubility and proteolytic processing. Steady state analysis of an unfolding experiment as monitored by circular dichroism and fluorescence spectroscopy demonstrated a typical two-state transition. The determined unfolding free energy for the L175V mutant revealed a structural destabilization of 10.49 kcal/mol relative to the wild type. However unfolding kinetic analysis gave identical activation energy for wild type and both mutants. Our findings suggested that a perturbation on the close packing of the hydrophobic side chains in protein interior could lead to a significant destabilization of the native conformation.