Membrane protein biogenesis by the EMC

Alvira, Sara; Corey, Robin A.; Collinson, Ian; Römisch, Karin

doi:10.15252/embj.2020107407

Cited by 10 publications

(10 citation statements)

References 12 publications

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“…However, the Emc6–Emc3 core region with their 6 transmembrane domains are sufficient to promote protein insertion. This observation confirms the insertion mechanism that was proposed on the basis of recent cryo-electron microscopic studies that revealed that a membrane-embedded hydrophobic groove formed by Emc3 and Emc6 constitutes a transient binding site that incorporates transmembrane stretches into a disturbed and locally thinned lipid bilayer [ 35 – 37 , 52 , 53 ].…”

Section: Discussionsupporting

confidence: 87%

The ER membrane complex (EMC) can functionally replace the Oxa1 insertase in mitochondria

et al. 2022

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Two multisubunit protein complexes for membrane protein insertion were recently identified in the endoplasmic reticulum (ER): the guided entry of tail anchor proteins (GET) complex and ER membrane complex (EMC). The structures of both of their hydrophobic core subunits, which are required for the insertion reaction, revealed an overall similarity to the YidC/Oxa1/Alb3 family members found in bacteria, mitochondria, and chloroplasts. This suggests that these membrane insertion machineries all share a common ancestry. To test whether these ER proteins can functionally replace Oxa1 in yeast mitochondria, we generated strains that express mitochondria-targeted Get2–Get1 and Emc6–Emc3 fusion proteins in Oxa1 deletion mutants. Interestingly, the Emc6–Emc3 fusion was able to complement an Δoxa1 mutant and restored its respiratory competence. The Emc6–Emc3 fusion promoted the insertion of the mitochondrially encoded protein Cox2, as well as of nuclear encoded inner membrane proteins, although was not able to facilitate the assembly of the Atp9 ring. Our observations indicate that protein insertion into the ER is functionally conserved to the insertion mechanism in bacteria and mitochondria and adheres to similar topological principles.

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Section: Discussionsupporting

confidence: 87%

The ER membrane complex (EMC) can functionally replace the Oxa1 insertase in mitochondria

et al. 2022

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“…Extracts were produced by solubilising membranes with the detergent dodecyl-maltoside (DDM) and subsequently fractionated by size exclusion chromatography. We know from previous findings that cardiolipin (CL) is required to stabilise the associated states of SecYEG-SecDFyajC-YidC (the holo-translocon) as well as the holo-translocon-BAM super-complex [17–19], so we reasoned that if an even larger Sec-associated complexes existed in the envelope then they too would be stabilised by CL. Thus, the size-exclusion experiments were conducted with and without augmented CL in the column buffer (0.02 % (w/v) DDM ± 0.002 % (w/v) CL).…”

Section: Resultsmentioning

confidence: 99%

A bacterial secretosome for regulated envelope biogenesis and quality control

Watkins

Collinson

2022

Preprint

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As the first line of defence against antibiotics, the Gram-negative bacterial envelope and its biogenesis are of considerable interest to the microbiological and biomedical communities. All bacterial proteins are synthesised in the cytosol, so inner- and outer-membrane proteins, and periplasmic residents have to be transported to their final destinations via specialised protein machinery. The Sec translocon, a ubiquitous integral inner-membrane (IM) complex, is key to this process as the major gateway for protein transit from the cytosol to the cell envelope; this can be achieved during their translation, or afterwards. Proteins need to be directed to the inner-membrane (usually co-translational), otherwise SecA utilises ATP and the proton-motive-force (PMF) to drive proteins across the membrane post-translationally. These proteins are then picked up by chaperones for folding in the periplasm or delivered to the β-barrel assembly machinery (BAM) for incorporation into the outer-membrane. The core heterotrimeric SecYEG-complex forms the hub for an extensive network of interactions that regulate protein delivery and quality control. Here, we conduct a biochemical exploration of this secretosome: a very large, versatile and inter-changeable assembly with the Sec-translocon at its core; featuring interactions that facilitate secretion (SecDF), inner- and outer-membrane protein insertion (respectively, YidC and BAM), protein folding and quality control (e.g. PpiD, YfgM and FtsH). We propose the dynamic interplay amongst these and other factors act to ensure efficient whole envelope biogenesis, regulated to accommodate the requirements of cell elongation and division. This organisation would be essential for cell wall biogenesis and remodelling and thus its perturbation would be a good strategy for the development of anti-microbials.

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“…Simulations on the S . cerevisiae EMC structure have revealed that perturbations in the cytoplasmic leaflet of the ER bilayer facilitates flooding of the substrate binding pocket with water, promoting a hydrophilic environment instrumental to insertion [ 51 ]. Since PC and PE are major structural components of the ER membrane, it is tempting to speculate that the role of the TbEMC in lipid biosynthesis may be tied to the creation of a microenvironment conducive to TMD insertion, and thus TbEMC function.…”

Section: Discussionmentioning

confidence: 99%

The endoplasmic reticulum membrane protein complex localizes to the mitochondrial - endoplasmic reticulum interface and its subunits modulate phospholipid biosynthesis in Trypanosoma brucei

et al. 2022

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The endoplasmic reticulum membrane complex (EMC) is a versatile complex that plays a key role in membrane protein biogenesis in the ER. Deletion of the complex has wide-ranging consequences including ER stress, disturbance in lipid transport and organelle tethering, among others. Here we report the function and organization of the evolutionarily conserved EMC (TbEMC) in the highly diverged eukaryote, Trypanosoma brucei. Using (co-) immunoprecipitation experiments in combination with mass spectrometry and whole cell proteomic analyses of parasites after depletion of select TbEMC subunits, we demonstrate that the TbEMC is composed of 9 subunits that are present in a high molecular mass complex localizing to the mitochondrial-endoplasmic reticulum interface. Knocking out or knocking down of single TbEMC subunits led to growth defects of T. brucei procyclic forms in culture. Interestingly, we found that depletion of individual TbEMC subunits lead to disruption of de novo synthesis of phosphatidylcholine (PC) or phosphatidylethanolamine (PE), the two most abundant phospholipid classes in T. brucei. Downregulation of TbEMC1 or TbEMC3 inhibited formation of PC while depletion of TbEMC8 inhibited PE synthesis, pointing to a role of the TbEMC in phospholipid synthesis. In addition, we found that in TbEMC7 knock-out parasites, TbEMC3 is released from the complex, implying that TbEMC7 is essential for the formation or the maintenance of the TbEMC.

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Membrane protein biogenesis by the EMC

Cited by 10 publications

References 12 publications

The ER membrane complex (EMC) can functionally replace the Oxa1 insertase in mitochondria

The ER membrane complex (EMC) can functionally replace the Oxa1 insertase in mitochondria

A bacterial secretosome for regulated envelope biogenesis and quality control

The endoplasmic reticulum membrane protein complex localizes to the mitochondrial - endoplasmic reticulum interface and its subunits modulate phospholipid biosynthesis in Trypanosoma brucei

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