Abstract | BACKGROUND: Bacillus thuringiensis (Bt), an ubiquitous gram-positive spore-forming bacterium forms parasporal proteins during the stationary phase of its growth. Recent findings of selective human cancer cell-killing activity in non-insecticidal Bt isolates resulted in a new category of Bt parasporal protein called parasporin. However, little is known about the receptor molecules that bind parasporins and the mechanism of anti- cancer activity. A Malaysian Bt isolate, designated Bt18 produces parasporal protein that exhibit preferential cytotoxic activity for human leukaemic T cells (CEM-SS) but is non-cytotoxic to normal T cells or other cancer cell lines such as human cervical cancer (HeLa), human breast cancer (MCF-7) and colon cancer (HT-29) suggesting properties similar to parasporin. In this study we aim to identify the binding protein for Bt18 in human leukaemic T cells. METHODS: Bt18 parasporal protein was separated using Mono Q anion exchange column attached to a HPLC system and antibody was raised against the purified 68-kDa parasporal protein. Receptor binding assay was used to detect the binding protein for Bt18 parasporal protein in CEM-SS cells and the identified protein was sent for N-terminal sequencing. NCBI protein BLAST was used to analyse the protein sequence. Double immunofluorescence staining techniques was applied to localise Bt18 and binding protein on CEM-SS cell. RESULTS:
Anion exchange separation of Bt18 parasporal protein yielded a 68-kDa parasporal protein with specific cytotoxic activity. Polyclonal IgG (anti-Bt18) for the 68-kDa parasporal protein was successfully raised and purified. Receptor binding assay showed that Bt18 parasporal protein bound to a 36-kDa protein from the CEM-SS cells lysate. N-terminal amino acid sequence of the 36-kDa protein was GKVKVGVNGFGRIGG. NCBI protein BLAST revealed that the binding protein was Glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Double immunofluorescence staining showed co-localisation of Bt18 and GAPDH on the plasma membrane of the CEM-SS cells. CONCLUSIONS: GAPDH has been well known as a glycolytic enzyme, but recently GAPDH was discovered to have roles in apoptosis and carcinogenesis. Pre-incubation of anti-GAPDH antibody with CEM-SS cells decreases binding of Bt18 to the susceptible cells. Based on a qualitative analysis of the immunoblot and immunofluorescence results, GAPDH was identified as a binding protein on the plasma membrane of CEM-SS cells for Bt18 parasporal protein.
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Authors | Kanakeswary Krishnan, Jeremy Er An Ker, Shar Mariam Mohammed, Vishna Devi Nadarajah |
Journal | Journal of biomedical science
(J Biomed Sci)
Vol. 17
Pg. 86
(Nov 13 2010)
ISSN: 1423-0127 [Electronic] England |
PMID | 21073742
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Bacterial Proteins
- Endotoxins
- parasporin
- Glyceraldehyde-3-Phosphate Dehydrogenases
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Topics |
- Bacillus thuringiensis
(genetics, metabolism)
- Bacterial Proteins
(genetics, metabolism, pharmacology)
- Cell Line, Tumor
(drug effects)
- Endotoxins
(genetics, metabolism, pharmacology)
- Glyceraldehyde-3-Phosphate Dehydrogenases
(metabolism)
- Humans
- Leukemia
(metabolism)
- Protein Binding
- Spores, Bacterial
(chemistry, metabolism)
- T-Lymphocytes
(cytology, drug effects, metabolism)
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