The expression of Ad12 E1B 19K protein on the surface of adenovirus transformed and infected human cells.

Using radioimmunoassays we have confirmed earlier reports that the adenovirus 12 E1B 19K protein is expressed on the surface of transformed and infected human cells. Immunoprecipitation and radioimmunoassay of Ad 12 infected primary human embryo kidney cells demonstrated a considerable time lag in the translocation of the 19K protein to the external membrane after its expression within the cell. We have used antisera raised against synthetic octapeptides to detect and map the orientation of the polypeptide in the plasma membrane. The data obtained suggest that the C-terminus of the protein is exposed on the outside of the cell whereas the N-terminus is free in the cytoplasm. The predicted secondary structure of the 19K protein demonstrates a hydrophobic region which is highly conserved amongst Ad2, 5, 7 and 12 (amino acids 83-100 in Ad12) and we conclude that this forms the transmembrane domain. These observations are discussed in relation to the known functions of the Ad12 E1B 19K protein.