Members of the evolutionarily conserved Oxa1/Alb3/YidC family mediate membrane protein biogenesis at the mitochondrial inner membrane, chloroplast thylakoid membrane, and bacterial plasma membrane, ...respectively. Despite their broad phylogenetic distribution, no Oxa1/Alb3/YidC homologs are known to operate in eukaryotic cells outside the endosymbiotic organelles. Here, we present bioinformatic evidence that the tail-anchored protein insertion factor WRB/Get1, the “endoplasmic reticulum (ER) membrane complex” subunit EMC3, and TMCO1 are ER-resident homologs of the Oxa1/Alb3/YidC family. Topology mapping and co-evolution-based modeling demonstrate that Get1, EMC3, and TMCO1 share a conserved Oxa1-like architecture. Biochemical analysis of human TMCO1, the only homolog not previously linked to membrane protein biogenesis, shows that it associates with the Sec translocon and ribosomes. These findings suggest a specific biochemical function for TMCO1 and define a superfamily of proteins—the “Oxa1 superfamily”—whose shared function is to facilitate membrane protein biogenesis.
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•The “Oxa1 superfamily” comprises a group of membrane protein biogenesis factors•Three ER-resident proteins, Get1, EMC3, and TMCO1, are members of the superfamily•TMCO1, similar to bacterial YidC, associates with ribosomes and the Sec translocon
The absence of Oxa1/Alb3/YidC homologs in the eukaryotic endomembrane system has been a mystery. Now, Anghel et al. identify three ER-resident proteins, Get1, EMC3, and TMCO1, as remote homologs of Oxa1/Alb3/YidC proteins and show that TMCO1 possesses YidC-like biochemical properties. This defines the “Oxa1 superfamily” of membrane protein biogenesis factors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Optical spectroscopy in high magnetic fields B ≤ 65 T is used to reveal the very different nature of carriers in monolayer and bulk transition metal dichalcogenides. In monolayer WSe2, the exciton ...emission shifts linearly with the magnetic field and exhibits a splitting that originates from the magnetic field induced valley splitting. The monolayer data can be described using a single particle picture with a Dirac-like Hamiltonian for massive Dirac Fermions, with an additional term to phenomenologically include the valley splitting. In contrast, in bulk WSe2 where the inversion symmetry is restored, transmission measurements show a distinctly excitonic behavior with absorption to the 1s and 2s states. Magnetic field induces a spin splitting together with a small diamagnetic shift and cyclotron like behavior at high fields, which is best described within the hydrogen model.
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IJS, KILJ, NUK, PNG, UL, UM
Membrane proteins with multiple transmembrane domains play critical roles in cell physiology, but little is known about the machinery coordinating their biogenesis at the endoplasmic reticulum. Here ...we describe a ~ 360 kDa ribosome-associated complex comprising the core Sec61 channel and five accessory factors: TMCO1, CCDC47 and the Nicalin-TMEM147-NOMO complex. Cryo-electron microscopy reveals a large assembly at the ribosome exit tunnel organized around a central membrane cavity. Similar to protein-conducting channels that facilitate movement of transmembrane segments, cytosolic and luminal funnels in TMCO1 and TMEM147, respectively, suggest routes into the central membrane cavity. High-throughput mRNA sequencing shows selective translocon engagement with hundreds of different multi-pass membrane proteins. Consistent with a role in multi-pass membrane protein biogenesis, cells lacking different accessory components show reduced levels of one such client, the glutamate transporter EAAT1. These results identify a new human translocon and provide a molecular framework for understanding its role in multi-pass membrane protein biogenesis.
Cells possess specialized machinery to direct the insertion of membrane proteins into the lipid bilayer. In bacteria, the essential protein YidC inserts certain proteins into the plasma membrane, and ...eukaryotic orthologs are present in the mitochondrial inner membrane and the chloroplast thylakoid membrane. The existence of homologous insertases in archaea has been proposed based on phylogenetic analysis. However, limited sequence identity, distinct architecture, and the absence of experimental data have made this assignment ambiguous. Here we describe the 3.5-Å crystal structure of an archaeal DUF106 protein from Methanocaldococcus jannaschii (Mj0480), revealing a lipid-exposed hydrophilic surface presented by a conserved YidC-like fold. Functional analysis reveals selective binding of Mj0480 to ribosomes displaying a stalled YidC substrate, and a direct interaction between the buried hydrophilic surface of Mj0480 and the nascent chain. These data provide direct experimental evidence that the archaeal DUF106 proteins are YidC/Oxa1/Alb3-like insertases of the archaeal plasma membrane.
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•An archaeal DUF106 protein from M. jannaschii (Mj0480) adopts a YidC-like fold•Mj0480 binds selectively to stalled ribosome-nascent chain complexes•The nascent chain directly contacts a lipid-exposed hydrophilic surface of Mj0480•This work establishes the universality of YidC proteins in all three domains of life
YidC/Oxa1/Alb3 proteins are essential for the insertion of certain membrane proteins in bacteria and eukaryotes. Borowska et al. now describe an archaeal protein with structural and functional similarities to bacterial YidC. This work establishes the universality of the YidC/Oxa1/Alb3 family in the three domains of life.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Resonant Raman spectra of single-layer WS2 flakes are presented. A second-order Raman peak (2LA) appears under resonant excitation with a separation from the E12g mode of only 4cm−1. Depending on the ...intensity ratio and the respective linewidths of these two peaks, any analysis that neglects the presence of the 2LA mode can lead to an inaccurate estimation of the position of the E12g mode, leading to a potentially incorrect assignment for the number of layers. Our results show that the intensity of the 2LA mode strongly depends on the angle between the linear polarization of the excitation and detection, a parameter that is neglected in many Raman studies.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Context . Jupiter-family comets (JFCs), which originate from the Kuiper belt and scattered disk, exhibit low-inclination and chaotic trajectories due to close encounters with Jupiter. Despite their ...typically short incursions into the inner solar system, a notable number of them are on Earth-crossing orbits, with fireball networks detecting many objects on “JFC-like” (2 < T J < 3) orbits. Aims . This investigation aims to examine the orbital dynamics of JFCs and comet-like fireballs over 10 4 yr timescales, focusing on the trajectories and stability of these objects in the context of gravitational interactions within the solar system. Methods . We employed an extensive fireball dataset from Desert Fireball Network (DFN), European Fireball Network (EFN), Fireball Recovery and InterPlanetary Observation Network (FRIPON), and Meteorite Observation and Recovery Project (MORP), alongside telescopically observed cometary ephemeris from the NASA HORIZONS database. The study integrates 646 fireball orbits with 661 JFC orbits for a comparative analysis of their orbital stability and evolution. Results . The analysis confirms frequent Jupiter encounters among most JFCs, inducing chaotic orbital behavior with limited predictability and short Lyapunov lifetimes (~120 yr), underscoring Jupiter’s significant dynamical influence. In contrast, “JFC-like” meteoroids detected by fireball networks largely exhibit dynamics divergent from genuine JFCs, with 79–92% on “JFC-like” orbits shown not to be prone to frequent Jupiter encounters; in particular, only 1–5% of all fireballs detected by the four networks exhibit dynamics similar to that of actual JFCs. In addition, 22% (16 of 72) of near-Earth JFCs are on highly stable orbits, suggesting a potential main belt origin for some of the bodies. Conclusions . This extensive study delineates the stark dynamical contrast between JFCs and JFC-like meteoroids detected by global fireball networks. The majority of centimeter- and meter-scale meteoroids on JFC-like orbits exhibit remarkably stable trajectories, which starkly differ from the chaotic paths of their km-scale counterparts. Our findings suggest that the JFC-like objects observed by fireball networks predominantly originate from the outer main belt, with only a minor fraction being directly attributable to traditional JFCs.
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FMFMET, NUK, UL, UM, UPUK
This review article summarizes recent developments related to the dynamical formation of persistent spin helices in GaAs- and CdTe-based heterostructures. We start with fundamental aspects of ...spin-orbit interaction in quantum wells, in particular the Dresselhaus and Rashba terms and their relation to the bulk and structural inversion asymmetries, respectively. In the regime of balanced interactions, their combined impact gives rise to the formation of the persistent spin helix, i.e., a regime where a unidirectional spin grating with enhanced coherence time is established. The experimental scheme relies on ultrafast Kerr microscopy and permits to excite the spin polarization and detect it with a simultaneous spatial and temporal resolution of micrometers and picoseconds, respectively. For a microscopic understanding and a description of the results, kinetic theory of spatio-temporal spin dynamics of two-dimensional electrons is presented. In addition, Monte Carlo simulations of the spin distribution function are performed. Based on these concepts we discuss three areas with recent advances in the field of spin helices. (i) Anisotropic spin transport and spin helix dynamics in a modulation-doped GaAs quantum well is analyzed. It is observed that application of an out-of-plane electric field changes spin-orbit interaction through the Rashba component and the cubic Dresselhaus term. Remarkably, a weak in-plane electric field substantially increases spin diffusion and also affects the spin helix wavelength. (ii) In-plane magnetic fields applied in two perpendicular orientations allow for the extraction of the individual spin-orbit coupling parameters. (iii) Finally, we explore the influence of optical doping on the spin helix in a CdTe quantum well. Most importantly, a non-uniform spatio-temporal precession pattern is observed. The kinetic theory of spin diffusion allows us to model this finding by incorporating a dependence on the photo-carrier density into the Rashba and the Dresselhaus parameters.
Due to the oscillating behaviour of the pantograph and the catenary during the movement of the locomotive, the contact force changes to wide limits, resulting in electrical sparks with consequences: ...premature wear of the contact wire, electromagnetic disturbances, energy loss. Suitable control of the contact force at speeds exceeding 160 km/h may diminish these effects. Due to the particularities of the pantograph-catenary system and many random external factors, existing control methods do not always give the best results. The authors' research has shown that the contact force signal contains a chaotic component that can be offset by chaos theory methods. Their own studies have demonstrated theoretically and by simulation that this approach can largely eliminate the separating the pantograph from the catenary and will lessen excessive forces. Experimental research, conducted by the authors and presented in this article, has been done in laboratory conditions on a specially built test stand and confirms that this new approach to active pantograph control produces superior results to existing methods.
Analytical modeling of the flow of manufacturing process of the cement is difficult because of their complexity and has not resulted in sufficiently precise mathematical models. In this paper, based ...on a statistical model of the process and using the knowledge of human experts, was designed a fuzzy system for automatic control of clinkering process.
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