Dataset Information

The Escherichia coli Outer Membrane ?-Barrel Assembly Machinery (BAM) Anchors the Peptidoglycan Layer by Spanning It with All Subunits.

ABSTRACT: Gram-negative bacteria possess a three-layered envelope composed of an inner membrane, surrounded by a peptidoglycan (PG) layer, enclosed by an outer membrane. The envelope ensures protection against diverse hostile milieus and offers an effective barrier against antibiotics. The layers are connected to each other through many protein interactions. Bacteria evolved sophisticated machineries that maintain the integrity and the functionality of each layer. The ?-barrel assembly machinery (BAM), for example, is responsible for the insertion of the outer membrane integral proteins including the lipopolysaccharide transport machinery protein LptD. Labelling bacterial cells with BAM-specific fluorescent antibodies revealed the spatial arrangement between the machinery and the PG layer. The antibody detection of each BAM subunit required the enzymatic digestion of the PG layer. Enhancing the spacing between the outer membrane and PG does not abolish this prerequisite. This suggests that BAM locally sets the distance between OM and the PG layer. Our results shed new light on the local organization of the envelope.

SUBMITTER: Consoli E

PROVIDER: S-EPMC7918090 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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The <i>Escherichia coli</i> Outer Membrane β-Barrel Assembly Machinery (BAM) Anchors the Peptidoglycan Layer by Spanning It with All Subunits.

Consoli Elisa E Collet Jean-François JF den Blaauwen Tanneke T

International journal of molecular sciences 20210212 4

Gram-negative bacteria possess a three-layered envelope composed of an inner membrane, surrounded by a peptidoglycan (PG) layer, enclosed by an outer membrane. The envelope ensures protection against diverse hostile milieus and offers an effective barrier against antibiotics. The layers are connected to each other through many protein interactions. Bacteria evolved sophisticated machineries that maintain the integrity and the functionality of each layer. The β-barrel assembly machinery (BAM), fo ...[more]

PMID: 33673366

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Project description:The biogenesis of the outer membrane (OM) of Escherichia coli is a conserved and vital process. The assembly of integral ?-barrel outer membrane proteins (OMPs), which represent a major component of the OM, depends on periplasmic chaperones and the heteropentameric ?-barrel assembly machine (Bam complex) in the OM. However, not all OMPs are affected by null mutations in the same chaperones or nonessential Bam complex members, suggesting there are categories of substrates with divergent requirements for efficient assembly. We have previously demonstrated two classes of substrates, one comprising large, low-abundance, and difficult-to-assemble substrates that are heavily dependent on SurA and also Skp and FkpA, and the other comprising relatively simple and abundant substrates that are not as dependent on SurA but are strongly dependent on BamB for assembly. Here, we describe novel mutations in bamD that lower levels of BamD 10-fold and >25-fold without altering the sequence of the mature protein. We utilized these mutations, as well as a previously characterized mutation that lowers wild-type BamA levels, to reveal a third class of substrates. These mutations preferentially cause a marked decrease in the levels of multimeric proteins. This susceptibility of multimers to lowered quantities of Bam machines in the cell may indicate that multiple Bam complexes are needed to efficiently assemble multimeric proteins into the OM.The outer membrane (OM) of Gram-negative bacteria, such as Escherichia coli, serves as a selective permeability barrier that prevents the uptake of toxic molecules and antibiotics. Integral ?-barrel proteins (OMPs) are assembled by the ?-barrel assembly machine (Bam), components of which are conserved in mitochondria, chloroplasts, and all Gram-negative bacteria, including many clinically relevant pathogenic species. Bam is essential for OM biogenesis and accommodates a diverse array of client proteins; however, a mechanistic model that accounts for the selectivity and broad substrate range of Bam is lacking. Here, we show that the assembly of multimeric OMPs is more strongly affected than that of monomeric OMPs when essential Bam complex components are limiting, suggesting that multiple Bam complexes are needed to assemble multimeric proteins.

Dataset Information

The Escherichia coli Outer Membrane ?-Barrel Assembly Machinery (BAM) Anchors the Peptidoglycan Layer by Spanning It with All Subunits.

Publications

The <i>Escherichia coli</i> Outer Membrane β-Barrel Assembly Machinery (BAM) Anchors the Peptidoglycan Layer by Spanning It with All Subunits.

Similar Datasets

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