Characterization of the anti-cancer-cell parasporal proteins of a Bacillus thuringiensis isolate

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.