Abstract
Two cellular proteins, 61 and 37 kDa, are found in association with the simian virus 40 (SV40) small-t antigen. Fractionation in standard chromatography systems showed that these proteins were associated with one another in uninfected cells, suggesting that the small-t antigen may bind the complex as a whole and not each individual protein independently. In the presence of N-ethylmaleimide, the 37-kDA protein was selectively released from immune complexes, leaving the small-t antigen and 61-kDa protein in association. This result suggests that the small-t antigen may bind only the 61-kDa protein and that the 37-kDa protein may be associated with immune complexes by virtue of its association with the 61-kDa cellular protein.