Patent ID: 7662609

Claim:
An E. coli host cell expressing a recombinant antibody wherein the E. coli host cell has been genetically modified in order to change the isoelectric point of the E. coli Phosphate binding protein (PhoS/PstS) wherein the isoelectric point has been altered by: (a) the addition of a poly-aspartic acid tag to the C-terminus of the Phosphate binding protein and/or (b) changing one or more of the amino acid residues located on the surface of the E. coli Phosphate binding protein (PhoS/PstS) by (i) substituting one or more lysine and/or arginine residues with aspartic acid or a glutamic acid or (ii) substituting one or more aspartic acid and/or glutamic acid residues with lysine or arginine.