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Intermembrane crosstalk drives inner-membrane protein organization in Escherichia coli.

ABSTRACT: Gram-negative bacteria depend on energised protein complexes that connect the two membranes of the cell envelope. However, ?-barrel outer-membrane proteins (OMPs) and ?-helical inner-membrane proteins (IMPs) display quite different organisation. OMPs cluster into islands that restrict their lateral mobility, while IMPs generally diffuse throughout the cell. Here, using live cell imaging of Escherichia coli, we demonstrate that when transient, energy-dependent transmembrane connections are formed, IMPs become subjugated by the inherent organisation of OMPs and that such connections impact IMP function. We show that while establishing a translocon for import, the colicin ColE9 sequesters the IMPs of the proton motive force (PMF)-linked Tol-Pal complex into islands mirroring those of colicin-bound OMPs. Through this imposed organisation, the bacteriocin subverts the outer-membrane stabilising role of Tol-Pal, blocking its recruitment to cell division sites and slowing membrane constriction. The ordering of IMPs by OMPs via an energised inter-membrane bridge represents an emerging functional paradigm in cell envelope biology.

SUBMITTER: Rassam P

PROVIDER: S-EPMC5852019 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Intermembrane crosstalk drives inner-membrane protein organization in Escherichia coli.

Rassam Patrice P Long Kathleen R KR Kaminska Renata R Williams David J DJ Papadakos Grigorios G Baumann Christoph G CG Kleanthous Colin C

Nature communications 20180314 1

Gram-negative bacteria depend on energised protein complexes that connect the two membranes of the cell envelope. However, β-barrel outer-membrane proteins (OMPs) and α-helical inner-membrane proteins (IMPs) display quite different organisation. OMPs cluster into islands that restrict their lateral mobility, while IMPs generally diffuse throughout the cell. Here, using live cell imaging of Escherichia coli, we demonstrate that when transient, energy-dependent transmembrane connections are formed ...[more]

PMID: 29540681

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Project description:Biological membranes are essential for cell viability. Their functional characteristics strongly depend on their protein content, which consists of transmembrane (integral) and peripherally associated membrane proteins. Both integral and peripheral inner membrane proteins mediate a plethora of biological processes. Whereas transmembrane proteins have characteristic hydrophobic stretches and can be predicted using bioinformatics approaches, peripheral inner membrane proteins are hydrophilic, exist in equilibria with soluble pools, and carry no discernible membrane targeting signals. We experimentally determined the cytoplasmic peripheral inner membrane proteome of the model organism Escherichia coli using a multidisciplinary approach. Initially, we extensively re-annotated the theoretical proteome regarding subcellular localization using literature searches, manual curation, and multi-combinatorial bioinformatics searches of the available databases. Next we used sequential biochemical fractionations coupled to direct identification of individual proteins and protein complexes using high resolution mass spectrometry. We determined that the proposed cytoplasmic peripheral inner membrane proteome occupies a previously unsuspected ?19% of the basic E. coli BL21(DE3) proteome, and the detected peripheral inner membrane proteome occupies ?25% of the estimated expressed proteome of this cell grown in LB medium to mid-log phase. This value might increase when fleeting interactions, not studied here, are taken into account. Several proteins previously regarded as exclusively cytoplasmic bind membranes avidly. Many of these proteins are organized in functional or/and structural oligomeric complexes that bind to the membrane with multiple interactions. Identified proteins cover the full spectrum of biological activities, and more than half of them are essential. Our data suggest that the cytoplasmic proteome displays remarkably dynamic and extensive communication with biological membrane surfaces that we are only beginning to decipher.

Dataset Information

Intermembrane crosstalk drives inner-membrane protein organization in Escherichia coli.

Publications

Intermembrane crosstalk drives inner-membrane protein organization in Escherichia coli.

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