The excC gene of Escherichia coli K‐12 required for cell envelope integrity encodes the peptidoglycan‐associated lipoprotein (PAL)

Abstract

The excC mutants of Escherichia coli are hypersensitive to drugs such as cholic acid and release periplasmic proteins into the extracellular medium. A 1884 bp fragment carrying the excC gene was isolated and sequenced. It contains the 3' end of the tolB gene which maps at min 17 on the E. coli map and an open reading frame which encodes the 18,748 Da ExcC protein. The protein is composed of a hydrophobic region of 22 residues and displayed an overall hydrophilic configuration. It was shown that the ExcC protein is indeed the PAL (peptidoglycan-associated lipoprotein) described by Mizuno (1979). The pal gene had not yet been characterized on the E. coli linkage map since no obvious phenotype could be identified for mutations in this gene. A topologic analysis of the PAL protein using PAL-PhoA translational fusions showed that PAL is associated with the outer membrane only by its N-terminal moiety. The carboxy-terminal part of the protein is necessary for correct interaction of PAL with the peptidoglycan layer.

Colicin Biology

“…TolB is a periplasmic protein that peripherally associates with the outer membrane (291). Pal is an abundant (ϳ25,000 copies per cell) (75) lipoprotein anchored to the outer membrane via its N-terminal acylated residue, and it interacts with the peptidoglycan layer through a conserved domain (residues 86 to 110) also found in the OmpA and MotB protein families (143,218,350,393,460).…”

Structure and evolution of the Ivy protein family, unexpected lysozyme inhibitors in Gram-negative bacteria

“…We then constructed a double mutant by introducing a TolB-pal deletion to reproduce the ''porous cell-wall'' phenotype described earlier (10). It was previously shown that E. coli ⌬tolB mutants exhibit a typical phenotype of sensitivity to drugs and detergents, leakiness, and outer membrane vesicles formation (10,11), because of impaired envelope synthesis. We measured the sensitivity to lysozyme of the ⌬tolB⌬ivy double mutant with reference to the ⌬tolB mutant (JC864).…”

Envelope instability in DNA adenine methylase mutants of Salmonella enterica

“…That is the case for the Braun's (murein) lipoprotein (Lpp) ; the peptidoglycan-associated lipoprotein (PAL) (Lazzaroni & Portalier, 1992) ; the periplasmic protein TolB ; and the inner-membrane complex formed by TolQ, TolR and TolA proteins (Lazzaroni et al, 1999). A series of studies have provided evidence for the existence of large complexes containing these proteins that establish a physical link between the inner and the outer membrane (Bouveret et al, 1995(Bouveret et al, , 1999Rigal et al, 1997 ;Clavel et al, 1998 ;Lazzaroni et al, 1999).…”