The expression of hepatitis C virus (HCV) E1 protein is toxic for Escherichia coli cells. For this reason, we have cloned the E1 gene in the pET3a vector and analyzed the inducible expression of the protein in two strains of E. coli characterised by a different level of reduction of basal synthesis. The results indicated that synthesis of E1 was supported only by the BL21(DE3)pLysS strain which provides a tightest control of protein expression before the induction. The BL21(DE3)pLysS cells were then used for the expression of E1 gene, varying at its carboxy terminus in order to retain (E1, aa 192-383) or delete (Elt, aa 192-340) a C-terminal hydrophobic region that may be involved in membrane association. Following cell fractionation, E1 protein was found associated with the membrane fraction. By contrast, the truncated mutant E1t, was identified in the soluble phase suggesting a direct role for the C-terminal domain in E1 membrane association.