Abstract: A modified portal protein of a bacteriophage DNA packaging motor, wherein the modified portal protein is capable of direct insertion into a membrane and wherein the portal protein is modified compared to the wild type portal protein such that one or more amino acid residues on the outer surface of the portal protein is substituted by one or more other amino acid residue, and/or wherein a one or more amino acid residue is inserted on the outer surface of the portal protein so as to alter the outer surface hydrophobicity of the modified portal protein compared to the wild type portal protein.