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Characterization of the anti-cancer-cell parasporal proteins of a Bacillus thuringiensis isolate
S Yamashita1, T Akao, E Mizuki
1Biotechnology and Food Research Institute, Fukuoka Industrial Technology Centre, Japan.
Abstract:
An unusual activity, associated with non-insecticidal and non-haemolytic parasporal inclusion proteins of a Bacillus thuringiensis soil isolate, designated 89-T-26-17, was characterized. The parasporal inclusion of this isolate was bipyramidal, rounded at both ends, containing proteins of 180, 150, 120, 100, and 88 kDa. No homologies with the Cry and Cyt proteins of B. thuringiensis were detected based on N-terminal sequences. Proteolytic processing of the inclusion proteins by proteinase K, trypsin, and chymotrypsin produced a major protein of 64 kDa exhibiting cytocidal activity against human leukaemic T cells and uterus cervix cancer (HeLa) cells. The protease-activated proteins showed no cytotoxicity to normal T cells.
Insights
Bacillus thuringiensis soil isolate proteins, distinct from known toxins, show potent cytocidal activity. Protease-activated proteins selectively target cancer cells, sparing normal cells.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bacillus thuringiensis (B.t.) produces parasporal inclusions with insecticidal and hemolytic activities.
- The specific isolate 89-T-26-17 contains unique parasporal inclusion proteins lacking homology to known B.t. Cry and Cyt toxins.
Purpose of the Study:
- To characterize the unusual activity of non-insecticidal and non-hemolytic parasporal inclusion proteins from B.t. isolate 89-T-26-17.
- To investigate the cytotoxic potential of these proteins against cancer cells.
Main Methods:
- Characterization of parasporal inclusion protein composition (180, 150, 120, 100, and 88 kDa).
- N-terminal sequencing to assess homology with known B.t. toxins.
- Proteolytic processing of inclusion proteins using proteinase K, trypsin, and chymotrypsin.
- Cytotoxicity assays against human leukaemic T cells and HeLa cells, and normal T cells.
Main Results:
- Parasporal inclusion proteins from isolate 89-T-26-17 showed no homology to Cry and Cyt proteins.
- Proteolytic processing generated a 64 kDa protein with significant cytocidal activity.
- This 64 kDa protein demonstrated selective cytotoxicity against human leukaemic T cells and HeLa cancer cells.
- No cytotoxicity was observed against normal T cells, indicating specificity.
Conclusions:
- The study identified novel B.t. parasporal proteins with unique characteristics.
- Protease-activated proteins from this isolate exhibit selective cytocidal activity against cancer cells.
- These findings suggest potential applications for these proteins in targeted cancer therapy.