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The antigenic sites of trichosanthin, a ribosome-inactivating protein with multiple pharmacological properties
1Department of Biochemistry, The Chinese University of Hong Kong, Shatin, NT.
Abstract:
Trichosanthin (TCS) fragments were produced by Tn1000 deletion mutagenesis and by cyanogen bromide (CNBr) cleavage and their immunoreactivity was examined by incubating with various antibodies. Twelve C-terminally truncated TCS variants were successfully synthesized under the control of a T7 RNA driven promoter. The smallest antigenic fragment mapped corresponded to the N-terminal 20 amino acids (aa). Six CNBr fragments of TCS were created and identified by electrospray mass spectrometry and N-terminal sequencing. Three antigenic fragments corresponding to aa 1-72, 101-152 and 153-246, respectively were mapped. Fragments corresponding to aa 1-72 and 153-246 were immunoreactive to the same monoclonal antibody showing they are components of a discontinuous epitope. On the other hand, the fragment containing aa 73-100 was not detected by any of the antibodies used.
Insights
Researchers identified key fragments of Trichosanthin (TCS) using mutagenesis and chemical cleavage. The smallest antigenic fragment spans the first 20 amino acids, revealing crucial details about TCS immunoreactivity.
Area of Science:
- Biochemistry
- Immunology
- Molecular Biology
Background:
- Trichosanthin (TCS) is a ribosome-inactivating protein with potential therapeutic applications.
- Understanding the immunoreactive regions of TCS is crucial for developing targeted therapies and diagnostic tools.
Purpose of the Study:
- To map the antigenic determinants of Trichosanthin (TCS).
- To identify specific fragments of TCS that elicit an immunoreactive response.
- To characterize the nature of epitopes within the TCS protein.
Main Methods:
- Production of C-terminally truncated TCS variants via Tn1000 deletion mutagenesis.
- Generation of TCS fragments using cyanogen bromide (CNBr) cleavage.
- Immunoreactivity assessment through antibody incubation.
- Identification of protein fragments using electrospray mass spectrometry and N-terminal sequencing.
Main Results:
- The smallest antigenic fragment of TCS was mapped to the N-terminal 20 amino acids.
- Three immunoreactive CNBr fragments were identified, corresponding to amino acids 1-72, 101-152, and 153-246.
- Fragments aa 1-72 and 153-246 reacted with the same monoclonal antibody, indicating a discontinuous epitope.
- The fragment containing amino acids 73-100 showed no immunoreactivity with the antibodies used.
Conclusions:
- Specific N-terminal and internal fragments of TCS contain important antigenic sites.
- A discontinuous epitope is formed by amino acids within the 1-72 and 153-246 regions.
- The 73-100 amino acid region of TCS does not appear to contain major B-cell epitopes recognized by the tested antibodies.