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Crystallization and preliminary X-ray diffraction studies of the 51 kDa protein of the mosquito-larvicidal binary
C Chiou1, E W Davidson, T Thanabalu
1Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA.
Abstract:
Certain strains of Bacillus sphaericus produce a highly toxic mosquito-larvicidal protein during sporulation which is active against vectors of dengue, encephalitis and malaria. This toxin is initially expressed as 51 and 42 kDa proteins and is converted to 43 and 39 kDa proteins, respectively, which form the active heterodimer complex. For a better understanding of the toxicity mechanism at the molecular level, the 51 kDa protein of the binary toxin of B. sphaericus strain 2297 was expressed as a glutathione-S-transferase fusion protein and purified by affinity chromatography. Protein crystals were grown from an amorphous precipitate in five months using the hanging-drop vapor-diffusion method. The protein crystals were dissolved and were found to be composed of a proteolytically modified 45.2 kDa derivative similar to the active form of this protein. The crystals form in space group P43212 (or P41212) and diffract to 2.6 A, with unit-cell dimensions a = b = 133.48, c = 69. 76 A.
Insights
Bacillus sphaericus produces a potent mosquito-larvicidal binary toxin. Researchers crystallized and characterized a key component, aiding understanding of its molecular toxicity mechanism against disease vectors.
Area of Science:
- Biochemistry
- Molecular Biology
- Crystallography
Background:
- Bacillus sphaericus produces a binary toxin highly effective against mosquito vectors of dengue, encephalitis, and malaria.
- The toxin is initially expressed as 51 and 42 kDa proteins, converting to 43 and 39 kDa active heterodimer components.
Purpose of the Study:
- To elucidate the molecular toxicity mechanism of the Bacillus sphaericus binary toxin.
- To obtain structural insights into the active form of the toxin.
Main Methods:
- Expression and purification of the 51 kDa protein of the B. sphaericus strain 2297 binary toxin as a glutathione-S-transferase fusion protein.
- Purification via affinity chromatography.
- Protein crystallization using the hanging-drop vapor-diffusion method over five months.
- X-ray diffraction analysis of the protein crystals.
Main Results:
- The 51 kDa protein was successfully expressed and purified.
- Crystals of a proteolytically modified 45.2 kDa derivative, similar to the active toxin form, were obtained.
- The crystals belong to space group P43212 (or P41212) and diffract to 2.6 Å resolution.
- Unit-cell dimensions were determined as a = b = 133.48 Å, c = 69.76 Å.
Conclusions:
- The structural characterization of the B. sphaericus binary toxin provides a foundation for understanding its mosquito-larvicidal activity.
- This research facilitates the development of novel strategies for controlling disease vectors like mosquitoes.