Expression of the adenovirus E1B 175R protein and its association with membranes of Escherichia coli

The E1B 175-amino-acid (175R) protein of adenovirus 2 is required for cellular transformation of primary cells and establishing cell morphology in lytically infected cells. To investigate the biochemical function of this protein, we constructed a bacterial expression vector (pKHB1-T) to produce the 175R protein in sufficient amounts for purification and biochemical analysis. On the basis of DNA sequencing, gel electrophoresis, and immunoblot analysis, the pKHB1-T-encoded 175R protein appears to be identical to that expressed transiently in mammalian or adenovirus-transformed cells. The bacterially produced viral protein was also found to be quite stable and without any modifications. Partial purification of the pKHB1-T-encoded protein revealed that the majority of its associates with the inner membrane of the bacterial cell. This, together with the possibility of the 175R protein containing an N-terminal amphipathic alpha-helix as a potential translocation signal, suggests that there may be a common mechanism of protein transport operating in both eucaryotic and procaryotic systems.