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This article is part of the themed collection: Recent Open Access Articles, A metal–insulator transition is observed in spin–orbit-coupled IrO2 thin films upon reduction of the film thickness. In the epitaxially grown samples, the critical thickness (t ∼ 1.5–2.2 nm) is found to depend on growth orientation (001), (100) or (110). Interestingly from the applied point of view, the insulating behavior is found even in polycrystalline ultrathin films. By analyzing the experimental electrical response with various theoretical models, we find good fits to the Efros–Shklovskii-VRH and the Arrhenius-type behaviors, which suggests an important role of electron correlations in determining the electrical properties of IrO2. Our magnetic measurements also point to a significant role of magnetic order. Altogether, our results would point to a mixed Slater- and Mott-type of insulator., This work was partially supported by the Spanish MINECO projects MAT2014-54425-R (MINECO/FEDER, UE), MAT2017-82970-C2-R (AEI/FEDER, UE), MAT2017-83468-R (AEI/FEDER, UE), MAT2017-87134-C02-01-R (AEI/FEDER, UE) and MAT2017-87134-C02-02-R (AEI/FEDER, UE), the Spanish MICINN project PID2020-115159GB-I00 / AEI / 10.13039/501100011033 and by the Aragon Regional Government (Projects No. E12-20R and E28-20R). E. A-E acknowledges the Spanish MINECO and the European Social Fund for an FPI (Formación de Personal Investigador, 2015) grant. R. B. acknowledges funding support from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 665919. This research used resources of the APS, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We acknowledge Diamond Light Source for time on I20-Scanning under Proposal SP-17266. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation Horizon 2020. The authors acknowledge funding from the project Quantox of QuantERA ERA-NET Cofund of Quantum Technologies (Grant Agreement No. 731473) implemented within the European Union's Horizon 2020 Programme.

4 pags., 9 figs., 2 tabs., The β-adrenoceptor (βAR) is a G-protein-coupled receptor (GPCR) that couples to the heterotrimeric G protein G. G-protein-mediated signalling is terminated by phosphorylation of the C terminus of the receptor by GPCR kinases (GRKs) and by coupling of β-arrestin 1 (βarr1, also known as arrestin 2), which displaces G and induces signalling through the MAP kinase pathway. The ability of synthetic agonists to induce signalling preferentially through either G proteins or arrestins—known as biased agonism—is important in drug development, because the therapeutic effect may arise from only one signalling cascade, whereas the other pathway may mediate undesirable side effects. To understand the molecular basis for arrestin coupling, here we determined the cryo-electron microscopy structure of the βAR–βarr1 complex in lipid nanodiscs bound to the biased agonist formoterol, and the crystal structure of formoterol-bound βAR coupled to the G-protein-mimetic nanobody Nb80. βarr1 couples to βAR in a manner distinct to that of G coupling to βAR—the finger loop of βarr1 occupies a narrower cleft on the intracellular surface, and is closer to transmembrane helix H7 of the receptor when compared with the C-terminal α5 helix of G. The conformation of the finger loop in βarr1 is different from that adopted by the finger loop of visual arrestin when it couples to rhodopsin. βAR coupled to βarr1 shows considerable differences in structure compared with βAR coupled to Nb80, including an inward movement of extracellular loop 3 and the cytoplasmic ends of H5 and H6. We observe weakened interactions between formoterol and two serine residues in H5 at the orthosteric binding site of βAR, and find that formoterol has a lower affinity for the βAR–βarr1 complex than for the βAR–G complex. The structural differences between these complexes of βAR provide a foundation for the design of small molecules that could bias signalling in the β-adrenoceptors., Work in the C.G.T. laboratory was funded by a grant from the European Research Council (EMPSI 339995), Heptares Therapeutics Ltd and core funding from the Medical Research Council (MRC U105197215). The research program in the A.K.S. laboratory is supported by an Intermediate Fellowship of the Wellcome Trust/DBT India Alliance Fellowship (grant number IA/I/14/1/501285), the Science and Engineering Research Board (SERB) (EMR/2017/003804), Innovative Young Biotechnologist Award from the Department of Biotechnology (DBT) (BT/08/IYBA/2014-3) and the Indian Institute of Technology, Kanpur. H.D.-A. is supported by the National PostDoctoral Fellowship of SERB (PDF/2016/002930) and DBT-BioCaRE grant (BT/PR31791/BIC/101/1228/2019). We thank Diamond Light Source (UK) for access and support of the cryo-EM facilities at eBIC (proposal EM17434) funded by the Wellcome Trust, MRC and BBSRC. We thank the beamline staff at the European Synchrotron Radiation Facility MASSIF-1 for help with X-ray diffraction data collection; T. Nakane, S. Monteleone and P. Kolb for discussions; D. Gloriam for access to unreleased data from GPCRdb; and G. Cannone from the LMB EM facility and J. Grimmett and T. Darling from LMB Scientific Computing for technical support during this work.

2 Schemes, 3 Tables, 5 Figures., A high surface area mesoporous TiO2 material (110 m2/g) was synthesised using a nanocasting methodology, utilizing SBA‐15 as a hard template. This material was subsequently used as a support to prepare a series of 1 wt.% AuPt/TiO2 catalysts, synthesised by conventional impregnation and sol‐immobilisation. Catalysts were tested for the oxidation of glycerol to lactic acid and their performance was compared with corresponding catalysts supported on TiO2−P25, TiO2‐anatase and TiO2‐rutile. Higher rates of reaction and higher selectivity to lactic acid were observed over nanocast TiO2 supported catalysts. The increased performance of these catalysts was attributed to the presence of Si on the surface of the support, which likely arose from inefficient etching of the SBA‐15 template. The presence of Si in these catalysts was confirmed by X‐ray photoelectron spectroscopy and electron energy loss spectroscopy. It was proposed that the residual Si present increases the Brønsted acidity of the TiO2 support, which can lead to the formation of Lewis acid sites under reaction conditions; both sites are known to catalyse the dehydration of a primary alcohol in glycerol. Typically, under alkaline conditions, lactic acid is formed by the nucleophilic abstraction of a hydrogen. Thus, we propose that the improved selectivity to lactic acid over the nanocast TiO2 supported catalyst is attributed to the co‐operation of heterogeneous and homogeneous dehydration reactions, as both compete directly with a direct oxidation pathway, which leads to the formation of oxidation products such as glyceric and tartronic acid., T. García would like to acknowledge the Spanish MICINN through its Mobility program for stays of senior researchers and professors in foreign countries (grant number PRX18/00474) for funding. O.S.P acknowledges the FPI fellowship (BES-2016-077750) funded by Spanish MINECO. B.S. also thank MINECO (MAT2017-84118-C2-1-R project) for funding. We would also like to thank the Cardiff University TEM facility for the TEM and FEG-SEM electron microscopy data acquired and Diamond Light Source for access and support in use of the electron Physical Science Imaging Centre (Instrument E01 and proposal number MG21641 and MG22766) which contributed to the results presented here.

Recent reports indicate that the Type six secretion system exported effector 8 (Tse8) is a cytoactive effector secreted by the Type VI secretion system (T6SS) of the human pathogen Pseudomonas aeruginosa. The T6SS is a nanomachine that assembles inside of the bacteria and injects effectors/toxins into target cells, providing a fitness advantage over competing bacteria and facilitating host colonisation. Here we present the first crystal structure of Tse8 revealing that it conserves the architecture of the catalytic triad Lys84-transSer162-Ser186 that characterises members of the Amidase Signature superfamily. Furthermore, using binding affinity experiments, we show that the interaction of phenylmethylsulfonyl fluoride (PMSF) to Tse8 is dependent on the putative catalytic residue Ser186, providing support for its nucleophilic reactivity. This work thus demonstrates that Tse8 belongs to the Amidase Signature (AS) superfamily. Furthermore, it highlights Tse8 similarity to two family members: the Stenotrophomonas maltophilia Peptide Amidase and the Glutamyl-tRNAGln amidotransferase subunit A from Staphylococcus aureus., This work was supported by the Ministerio de Economía y Competitividad (MINECO) Contract CTQ2016-76941-R, the Fundación Biofísica Bizkaia, the Basque Excellence Research Centre (BERC) program of the Basque Government, and Fundación BBVA (to DAJ). MASP acknowledges support by the MINECO under the “Juan de la Cierva Postdoctoral program” (position FJCI-2015-25725). PF acknowledges support by the Marie Curie Action Career Integration Grant (PCIG14-GA-2013-632072), the Ministerio de Economía y Competitividad Grant (MINECO, CTQ2017-82222-R) and thanks MINECO for the Severo Ochoa Excellence Accreditation (SEV-2016-0644). We acknowledge Diamond Light Source, ALBA synchrotron beamline BL13-XALOC, their staff, and iNEXT (proposals 1618/2538) for providing access to synchrotron radiation facilities. Dr Laura M. Nolan and Prof. Alain Filloux are gratefully acknowledged for helpful discussions.

The emergence of ferromagnetism in Rashba systems, where the evolving exchange interaction enters into competition with spin-orbit coupling, leads to a nontrivial spin-polarized electronic landscape with an intricate momentum-dependent spin structure, which is challenging to unveil. Here, we show a way to disentangle the contributions from the effective spin-orbit and exchange fields and thus to gain knowledge of the spin structure in ferromagnetic Rashba materials, which is required for spintronic applications. Our approach is based exclusively on spin-integrated photoemission measurements combined with a two-band modeling. As an example, we consider the mixed-valent material EuIr2Si2 which, while being nonmagnetic in the bulk, reveals strong ferromagnetism at the iridium-silicide surface where both spin-orbit and exchange magnetic interactions coexist. The combined effect of these interactions causes a complex band dispersion of the surface state which can be observed in photoemission experiments. Our method allows us to comprehensively unravel the surface-state spin structure driven by spin-orbit coupling at the ferromagnetic surface. This approach opens up opportunities to characterize the spin structure of ferromagnetic Rashba materials, especially where dedicated spin-resolved measurements remain challenging., This work was supported by Saint Petersburg State University (Grant No. ID 51126254) and the Russian Foundation for Basic Research (Grant No. 20-32-70127). We acknowledge financial support from the Spanish Ministry of Economy (No. MAT-2017-88374-P) and the German Research Foundation (DFG) through Grants No. LA655/20-1, No. KR3831/5-1, and Fermi-NEst. We acknowledge Diamond Light Source for access to beamline I05 (Proposals No. SI18844-1 and No. SI17761-1).

© The Author(s) 2019., Some molecular chaperones are involved not only in assisting the folding of proteins but also, given appropriate conditions, in their degradation. This is the case for Hsp70 and Hsp90 which, in concert with the cochaperone CHIP, direct their bound substrate to degradation through ubiquitination. We generated complexes between the chaperones (Hsp70 or Hsp90), the cochaperone CHIP and, as substrate, a p53 variant containing the GST protein (p53-TMGST). Both ternary complexes (Hsp70:p53-TMGST:CHIP and Hsp90:p53-TMGST:CHIP) ubiquitinated the substrate at a higher efficiency than in the absence of the chaperones. The 3D structures of the two complexes, obtained using a combination of cryoelectron microscopy and crosslinking mass spectrometry, showed the substrate located between the chaperone and the cochaperone, suggesting a ubiquitination mechanism in which the chaperone-bound substrate is presented to CHIP. These complexes are inherently flexible, which is important for the ubiquitination process., This research was supported by the grant BFU2016-75984 (AEI/FEDER, EU) to JMV. We thank Diamond Light Source for access to beamline EM16943 and EM15997 that contributed to the results presented here. The CRG/UPF Proteomics Unit is a member of Proteored, PRB3 and is supported by grant PT17/0019, of the PE I + D + i 2013–2016, funded by ISCIII and ERDF. We acknowledge support from the Spanish Ministry of Economy and Competitiveness, “Centro de Excelencia Severo Ochoa 2013–2017”, SEV-2012–0208, and “Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya” (2017SGR595).

The eukaryotic ubiquitylation machinery catalyzes the covalent attachment of the small protein modifier ubiquitin to cellular target proteins in order to alter their fate. Microbial pathogens exploit this post-translational modification process by encoding molecular mimics of E3 ubiquitin ligases, eukaryotic enzymes that catalyze the final step in the ubiquitylation cascade. Here, we show that the Legionella pneumophila effector protein RavN belongs to a growing class of bacterial proteins that mimic host cell E3 ligases to exploit the ubiquitylation pathway. The E3 ligase activity of RavN was located within its N-terminal region and was dependent upon interaction with a defined subset of E2 ubiquitin-conjugating enzymes. The crystal structure of the N-terminal region of RavN revealed a U-box-like motif that was only remotely similar to other U-box domains, indicating that RavN is an E3 ligase relic that has undergone significant evolutionary alteration. Substitution of residues within the predicted E2 binding interface rendered RavN inactive, indicating that, despite significant structural changes, the mode of E2 recognition has remained conserved. Using hidden Markov model-based secondary structure analyses, we identified and experimentally validated four additional L. pneumophila effectors that were not previously recognized to possess E3 ligase activity, including Lpg2452/SdcB, a new paralog of SidC. Our study provides strong evidence that L. pneumophila is dedicating a considerable fraction of its effector arsenal to the manipulation of the host ubiquitylation pathway., Author summary Bacterial pathogens often hijack conserved host pathways by encoding proteins that are molecular mimics of eukaryotic enzymes, thus tricking the host cell into surrendering its resources to the bacteria. Here, we show that the intracellular pathogen Legionella pneumophila uses such a strategy to exploit ubiquitylation, a conserved post-translational modification that is mediated by E3 ubiquitin ligases. L. pneumophila encodes molecular mimics of host E3 ligases, including the effector protein RavN, thereby subverting the ubiquitylation pathway for its own benefit during infection. Using protein crystallography, we show that the fold of RavN has only residual resemblance to conventional eukaryotic E3s, yet its mode of interaction with E2 enzymes, host proteins that are important for the ubiquitin transfer reaction, has been preserved throughout evolution. Inspired by the discovery of RavN, we performed an in silico fold homology search and discovered several additional E3 ligase candidates within the effector repertoire of L. pneumophila that, until now, had remained hidden due to lack of primary sequence similarity. Our study supports the hypothesis that E3 ligases are a vital part of the virulence program of L. pneumophila, and that these effectors, despite having undergone extensive evolutionary changes, have retained features that are critical for their biological function, including the ability to hijack host factors that are part of the ubiquitylation machinery.