Insight into the dual function of lipid phosphate phosphatase PgpB involved in two essential cell-envelope metabolic pathways in Escherichia coli

Xudong Tian,Frédéric Kerff,Guillaume Manat,Dominique Mengin-Lecreulx,Thierry Touzé,Rodolphe Auger

doi:10.1038/s41598-020-70047-5

Abstract

Ubiquitous PAP2 lipid phosphatases are involved in a wide array of central physiological functions. PgpB from Escherichia coli constitutes the archetype of this subfamily of membrane proteins. It displays a dual function by catalyzing the biosynthesis of two essential lipids, the phosphatidylglycerol (PG) and the undecaprenyl phosphate (C55-P). C55-P constitutes a lipid carrier allowing the translocation of peptidoglycan subunits across the plasma membrane. PG and C55-P are synthesized in a redundant manner by PgpB and other PAP2 and/or unrelated membrane phosphatases. Here, we show that PgpB is the sole, among these multiple phosphatases, displaying this dual activity. The inactivation of PgpB does not confer any apparent growth defect, but its inactivation together with another PAP2 alters the cell envelope integrity increasing the susceptibility to small hydrophobic compounds. Evidence is also provided of an interplay between PAP2s and the peptidoglycan polymerase PBP1A. In contrast to PGP hydrolysis, which relies on a His/Asp/His catalytic triad of PgpB, the mechanism of C55-PP hydrolysis appeared as only requiring the His/Asp diad, which led us to hypothesize distinct processes. Moreover, thermal stability analyses highlighted a substantial structural change upon phosphate binding by PgpB, supporting an induced-fit model of action.

Highlights

Undecaprenyl phosphate (C55-P) plays an essential role in the biogenesis of bacterial envelope polysaccharides such as the p eptidoglycan[1]
We showed that PgpB was the only one among Phosphatases of type 2 (PAP2) (i.e. PgpB, YbjG, LpxT ang YnbD) and other lipid phosphatases (i.e. BacA, PgpA and PgpC) from E. coli, being active on very distinct substrates and capable of supplying both C 55-P and PG simultaneously
PgpB forms an operon with two genes encoding LapA and LapB proteins, which are involved in controlling the biosynthesis of LPS to ensure the proper balance between LPS and phospholipids b iosyntheses[27,28,29]

Summary

Introduction

Undecaprenyl phosphate (C55-P) plays an essential role in the biogenesis of bacterial envelope polysaccharides such as the p eptidoglycan[1]. Four integral membrane enzymes catalyzing C55-PP hydrolysis have been identified in Escherichia coli: BacA, PgpB, YbjG and LpxT (formerly YeiU), which belong to two unrelated protein families: BacA and Phosphatidic Acid Phosphatases of type 2 (PAP2)[3,4,5] None of these enzymes is essential for growth, but the simultaneous knockout of bacA, pgpB and ybjG genes elicits a lethal phenotype due to a default of C 55-P supply[4]. The structures of soluble PAP2s were reported in their transition-state analog molybdate- and phosphate-bound forms[17,18] (Fig. 1B) Their catalytic cycle is initiated by a nucleophilic attack of the substrate phosphoryl group by the histidine residue from motif C3 (C3-His), leading to the covalent binding of a phosphate group to a nitrogen atom of the imidazole ring[19,20] (Fig. 1B). The C2-histidine is thought to act this time as a base to activate the water molecule

Methods

Results

Conclusion