Solubilization of SV40 Plasma‐Membrane‐Associated Large Tumor Antigen Using Single‐Phase Concentrations of 1‐Butanol

Abstract

The nature of the interaction of the simian virus 40 (SV40) transforming protein, large tumor antigen (T‐ag), with the plasma membrane of transformed cells is not well understood. We report here that SV40 plasma‐membrane‐associated large tumor antigen (pmT‐ag) can be solubilized by using single‐phase concentrations of 1‐butanol. Purified plasma membranes from SV40‐transformed mouse cells yielded T‐ag when treated with 2.5% butanol; solubilization of T‐ag from the purified membranes in butanol was temperature dependent, with approximately 10‐fold more T‐ag extracted at 37°C than at 22°C; and application of 2.5% butanol to mKSA cells after cellular surface proteins had been radiolabeled with 125I resulted in the release of iodinated T‐ag. Butanol‐extracted pmT‐ag coprecipitated with p53 and several cellular proteins ranging in size from 35 to 60 kDa. One cellular component migrated at a mobility similar to that of tubulin (56 kDa), and a monoclonal antibody against the a subunit of tubul