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Membrane D2 T antigen: characterization and comparison with its nuclear counterpart
1McGill Cancer Centre, Montréal, Que., Canada.
Summary
The adenovirus 2--simian virus 40 hybrid, Ad2+D2, produces membrane T antigen (D2 T antigen) that behaves like an integral membrane protein. This membrane-bound D2 T antigen forms a high molecular weight complex, distinct from its nuclear counterpart.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Adenovirus 2--simian virus 40 hybrid (Ad2+D2) produces T antigen.
- T antigen exists in both nuclear and membrane-associated forms.
Purpose of the Study:
- To characterize the biophysical properties of the membrane-associated D2 T antigen.
- To investigate the supramolecular structure of membrane-bound D2 T antigen.
Main Methods:
- Alkaline conditions (up to pH 11.5) were used to assess protein-membrane association.
- Solubilization was attempted using ionic and nonionic detergents.
- Sephacryl S-300 chromatography in high salt with Brij-99 was employed to analyze molecular weight differences.
Main Results:
- Up to 40% of membrane D2 T antigen remained associated with membranes under alkaline conditions.
- Complete solubilization was not achieved with detergents, suggesting integral membrane protein characteristics.
- Chromatography revealed the nuclear form dissociated into low molecular weight species, while the membrane form eluted as a high molecular weight complex.
Conclusions:
- Membrane D2 T antigen exhibits properties consistent with integral membrane proteins.
- The membrane form of D2 T antigen exists as a detergent-binding complex, differing in supramolecular structure from the nuclear form.