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Cellular localization and characterization of the Bacillus thuringiensis Orf2 crystallization factor.
N Staples1, D Ellar, N Crickmore
1Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
Current Microbiology
|May 31, 2001
Summary
Bacillus thuringiensis toxin Cry2Aa requires the Orf2 factor for in vivo crystallization. Orf2 facilitates Cry2Aa localization into cytoplasmic crystals, indicating a direct interaction essential for crystal formation.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bacillus thuringiensis produces insecticidal crystal proteins (Cry proteins) for pest control.
- The crystallization process of Cry proteins in vivo is not fully understood.
- Orf2 is an associated factor involved in Cry2Aa crystallization.
Purpose of the Study:
- To investigate the role of Orf2 in the in vivo crystallization of Bacillus thuringiensis Cry2Aa toxin.
- To determine the localization and interaction of Cry2Aa and Orf2 within the bacterial cell.
Main Methods:
- Co-expression of Cry2Aa and Orf2 in vivo.
- Expression of Cry2Aa and Orf2 individually in vivo.
- Cell fractionation and protein solubility assays.
- Analysis of protein localization via microscopy.
Main Results:
- Co-expression of Cry2Aa and Orf2 led to the formation of cuboidal cytoplasmic crystals.
- Orf2 alone was randomly distributed in the cytoplasm.
- Cry2Aa alone did not form visible crystals but remained soluble at high pH.
- Purified Orf2 co-precipitated with Cry2Aa, suggesting a direct interaction.
Conclusions:
- Orf2 is essential for the in vivo crystallization of Cry2Aa.
- Orf2 acts as a crystallization factor, promoting Cry2Aa localization and crystal formation.
- A direct interaction between Cry2Aa and Orf2 is crucial for the formation of insecticidal crystals.