A water-soluble form of penicillin-binding protein 2 of Escherichia coli constructed by site-directed mutagenesis.

Penicillin-binding protein (PBP) 2 of Escherichia coli is located in the cytoplasmic membrane. The N-terminal hydrophobic segment (31 amino acids, residues 15-45) of PBP2 was removed by a deletion in the PBP2 gene by site-directed mutagenesis, resulting in the production of a water-soluble form of PBP2 (called PBP2*). PBP2* retained the penicillin-binding activity, was localized in the cytoplasm and was overproduced under the control of the lpp-lac promoter. this indicates that the removed hydrophobic segment is an uncleaved signal sequence required for translocation of PBP2 across the cytoplasmic membrane, and also suggests that the segment anchors the protein to the membrane.