Analysis of the regulation of undecaprenyl diphosphate dephosphorylation in <i>Escherichia coli</i>

Undecaprenyl phosphate (C₅₅P) is an essential sugar carrier for bacterial cell wall synthesis, which has gained importance in recent years as a promising target for new antibiotic development. In Escherichia coli, C₅₅P is produced by dephosphorylation of undecaprenyl diphosphate (C₅₅PP) by BacA and two type 2 phosphatidic acid phosphatase (PAP2) family enzymes, PgpB and YbjG, in the periplasmic space. To clarify the regulatory mechanism of C₅₅PP dephosphorylation, we quantified C₅₅P and C₅₅PP using a new high-performance liquid chromatography method, conducted susceptibility tests against bacitracin, and analyzed the gene expression of bacA, pgpB, and ybjG in E. coli single- and double-disruption strains of those genes. C₅₅P levels were similar in all strains, but C₅₅PP levels increased only in the bacA, ybjG double-disruption strain. The double-disruption strains containing bacA disruption and the bacA single-disruption strain were more susceptible to bacitracin than the other strains. In the double-disruption strains containing bacA disruption, the expression of the remaining genes pgpB and ybjG increased. These results indicate that the transcription of the PAP2 family enzyme genes, pgpB and ybjG, was activated under conditions where C₅₅PP dephosphorylation activity in cells was reduced. This transcriptional regulation might contribute to the maintenance of C₅₅P levels in cells.