Expression of Semliki Forest virus E1 protein in Escherichia coli - Low pH-induced pore formation

Exposure of Semliki Forest virus 1 to mildly acidic conditions results in c onformational changes of the viral spike proteins, which in turn leads to a pore formation across its membrane. The ability to form a pore has been as cribed to the ectodomain of the Semliki Forest virus (SFV) E1 spike protein . To elucidate whether the E1 protein per se is sufficient for low pH-depen dent pore formation, we expressed E1 in Escherichia coli in an inducible ma nner using the pET11c expression system. The data obtained clearly showed t hat the E1 protein was expressed in the bacterial cell membrane and that ex posure of E. coli expressing the SFV E1 protein to low pH (< 6.2) resulted in a permeability change of the membrane. Thus, we conclude that the E1 pro tein of SFV per se is sufficient to promote pore formation under mildly aci dic conditions.