scholarly journals Small outer-membrane lipoprotein, SmpA, is regulated by σ E and has a role in cell envelope integrity and virulence of Salmonella enterica serovar Typhimurium

Microbiology ◽  
2008 ◽  
Vol 154 (3) ◽  
pp. 979-988 ◽  
Author(s):  
Claire Lewis ◽  
Henrieta Skovierova ◽  
Gary Rowley ◽  
Bronislava Rezuchova ◽  
Dagmar Homerova ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Cell Envelope ◽  
Outer Membrane Lipoprotein ◽  
Serovar Typhimurium ◽  
Membrane Lipoprotein

scholarly journals Roles of Internal Cysteines in the Function, Localization, and Reactivity of the TraV Outer Membrane Lipoprotein Encoded by the F Plasmid

2002 ◽  
Vol 184 (11) ◽  
pp. 3126-3129 ◽  
Author(s):  
Robin L. Harris ◽  
Philip M. Silverman
Keyword(s):  
Outer Membrane ◽  
Cell Envelope ◽  
Osmotic Shock ◽  
Wild Type ◽  
F Plasmid ◽  
Outer Membrane Lipoprotein ◽  
Numerous Cell ◽  
Mixed Disulfides ◽  
Membrane Lipoprotein

ABSTRACT We have examined the functional role of two internal cysteine residues of the F-plasmid TraV outer membrane lipoprotein. Each was mutated to a serine separately and together to yield three mutant traV genes: traV C10S, traV C18S, and traV C10S/C18S. All three cysteine mutations complemented a traV mutant for DNA donor activity and for sensitivity to donor-specific bacteriophage; however, when measured by a transduction assay, the donor-specific DNA bacteriophage sensitivities of the traV C18S and, especially, traV C10S/C18S mutant strains were significantly less than those of the traV + and traV C10S strains. Thus, unlike the Agrobacterium tumefaciens T-plasmid-encoded VirB7 outer membrane lipoprotein, TraV does not require either internal cysteine to retain significant biological activity. By Western blot analysis, all three mutant TraV proteins were shown to accumulate in the outer membrane. However, by nonreducing gel electrophoresis, wild-type TraV and especially the TraVC18S mutant were shown to form mixed disulfides with numerous cell envelope proteins. This was not observed with the TraVC10S or TraVC10S/C18S proteins. Thus, it appears that TraV C10 is unusually reactive and that this reactivity is reduced by C18, perhaps by intramolecular oxidation. Finally, whereas the TraVC10S and TraVC18S proteins fractionated primarily with the outer membrane, as did the wild-type protein, the TraVC10S/C18S protein was found in osmotic shock fluid and inner membrane fractions as well as outer membrane fractions. Hence, at least one cysteine is required for the efficient localization of TraV to the outer membrane.

scholarly journals Inhibition of Salmonella enterica Serovar Typhimurium Lipopolysaccharide Deacylation by Aminoarabinose Membrane Modification

2005 ◽  
Vol 187 (7) ◽  
pp. 2448-2457 ◽  
Author(s):  
Kiyoshi Kawasaki ◽  
Robert K. Ernst ◽  
Samuel I. Miller
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Bacterial Resistance ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Host Recognition ◽  
Membrane Modification ◽  
Serovar Typhimurium ◽  
Nonionic Detergent

ABSTRACT Salmonella enterica serovar Typhimurium remodels the lipid A component of lipopolysaccharide, a major component of the outer membrane, to survive within animals. The activation of the sensor kinase PhoQ in host environments increases the synthesis of enzymes that deacylate, palmitoylate, hydroxylate, and attach aminoarabinose to lipid A, also known as endotoxin. These modifications promote bacterial resistance to antimicrobial peptides and reduce the host recognition of lipid A by Toll-like receptor 4. The Salmonella lipid A 3-O-deacylase, PagL, is an outer membrane protein whose expression is regulated by PhoQ. In S. enterica serovar Typhimurium strains that had the ability to add aminoarabinose to lipid A, 3-O-deacylated lipid A species were not detected, despite the PhoQ induction of PagL protein expression. In contrast, strains defective for the aminoarabinose modification of lipid A demonstrated in vivo PagL activity, indicating that this membrane modification inhibited PagL's enzymatic activity. Since not all lipid A molecules are modified with aminoarabinose upon PhoQ activation, these results cannot be ascribed to the substrate specificity of PagL. PagL-dependent deacylation was detected in sonically disrupted membranes and membranes treated with the nonionic detergent n-octyl-β-d-glucopyranoside, suggesting that perturbation of the intact outer membrane releases PagL from posttranslational inhibition by aminoarabinose-containing membranes. Taken together, these results suggest that PagL enzymatic deacylation is posttranslationally inhibited by membrane environments, which either sequester PagL from its substrate or alter its conformation.

scholarly journals SciN Is an Outer Membrane Lipoprotein Required for Type VI Secretion in Enteroaggregative Escherichia coli

2008 ◽  
Vol 190 (22) ◽  
pp. 7523-7531 ◽  
Author(s):  
Marie-Stéphanie Aschtgen ◽  
Christophe S. Bernard ◽  
Sophie De Bentzmann ◽  
Roland Lloubès ◽  
Eric Cascales
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Biofilm Formation ◽  
Cell Envelope ◽  
Gene Clusters ◽  
Type Vi Secretion ◽  
Outer Membrane Lipoprotein ◽  
In Vivo Labeling ◽  
Membrane Lipoprotein

ABSTRACT Enteroaggregative Escherichia coli (EAEC) is a pathogen implicated in several infant diarrhea or diarrheal outbreaks in areas of endemicity. Although multiple genes involved in EAEC pathogenesis have been identified, the overall mechanism of virulence is not well understood. Recently, a novel secretion system, called type VI secretion (T6S) system (T6SS), has been identified in EAEC and most animal or plant gram-negative pathogens. T6SSs are multicomponent cell envelope machines responsible for the secretion of at least two putative substrates, Hcp and VgrG. In EAEC, two copies of T6S gene clusters, called sci-1 and sci-2, are present on the pheU pathogenicity island. In this study, we focused our work on the sci-1 gene cluster. The Sci-1 apparatus is probably composed of all, or a subset of, the 21 gene products encoded on the cluster. Among these subunits, some are shared by all T6SSs identified to date, including a ClpV-type AAA+ ATPase (SciG) and an IcmF (SciS) and an IcmH (SciP) homologue, as well as a putative lipoprotein (SciN). In this study, we demonstrate that sciN is a critical gene necessary for T6S-dependent secretion of the Hcp-like SciD protein and for biofilm formation. We further show that SciN is a lipoprotein, as shown by the inhibition of its processing by globomycin and in vivo labeling with [3H]palmitic acid. SciN is tethered to the outer membrane and exposed in the periplasm. Sequestration of SciN at the inner membrane by targeting the +2 residue responsible for lipoprotein localization (Gly2Asp) fails to complement an sciN mutant for SciD secretion and biofilm formation. Together, these results support a model in which SciN is an outer membrane lipoprotein exposed in the periplasm and essential for the Sci-1 apparatus function.

scholarly journals The apeE Gene of Salmonella enterica Serovar Typhimurium Is Induced by Phosphate Limitation and Regulated by phoBR

2001 ◽  
Vol 183 (5) ◽  
pp. 1784-1786 ◽  
Author(s):  
Christopher A. Conlin ◽  
Seng L. Tan ◽  
Huajun Hu ◽  
Todd Segar
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Phosphate Transport ◽  
Phosphate Limitation ◽  
Regulatory Locus ◽  
High Affinity ◽  
Serovar Typhimurium ◽  
Operon Expression

ABSTRACT Mutations in apeR, a regulatory locus of the outer membrane esterase apeE from Salmonella entericaserovar Typhimurium, were shown to be alleles of thepstSCAB-phoU high-affinity phosphate transport operon. Expression of apeE was induced by phosphate limitation, and this induction required the phoBR phosphate regulatory system.

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