Abstract
The questions of how the bulk of the Universe’s visible mass emerges and how it is manifest in the existence and properties of hadrons are profound, and probe the heart of strongly ...interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be key to a further understanding of the emergent mass and structure mechanisms. These mesons, namely, the pion and kaon, are the Nambu–Goldstone boson modes of quantum chromodynamics (QCD). Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches—continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions—linked to experimental measurements of hadron structure. Experimentally, the anticipated electron–ion collider will enable a revolution in our ability to study pion and kaon structures, accessed by scattering from the ‘meson cloud’ of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions that identify the critical detector-system requirements needed to map tagged pion and kaon cross-sections over a wide range of kinematics. The excellent prospects for extracting pion structural, functional, and form-factor data are outlined, and similar prospects for kaon structures are discussed in the context of a worldwide programme. The successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD’s Goldstone boson modes.
Whilst initial rates of insulin independence following islet transplantation are encouraging, long‐term function using the Edmonton Protocol remains a concern. The aim of this single‐arm, multicenter ...study was to evaluate an immunosuppressive protocol of initial antithymocyte globulin (ATG), tacrolimus and mycophenolate mofetil (MMF) followed by switching to sirolimus and MMF. Islets were cultured for 24 h prior to transplantation. The primary end‐point was an HbA1c of <7% and cessation of severe hypoglycemia. Seventeen recipients were followed for ≥12 months. Nine islet preparations were transported interstate for transplantation. Similar outcomes were achieved at all three centers. Fourteen of the 17 (82%) recipients achieved the primary end‐point. Nine (53%) recipients achieved insulin independence for a median of 26 months (range 7–39 months) and 6 (35%) remain insulin independent. All recipients were C‐peptide positive for at least 3 months. All subjects with unstimulated C‐peptide >0.2 nmol/L had cessation of severe hypoglycemia. Nine of the 17 recipients tolerated switching from tacrolimus to sirolimus with similar graft outcomes. There was a small but significant reduction in renal function in the first 12 months. The combination of islet culture, ATG, tacrolimus and MMF is a viable alternative for islet transplantation.
This multicenter Australian trial of islet transplantation alone, using antithymocyte globulin, tacrolimus, and mycophenolate mofetil, confi rms improving outcomes for the procedure and demonstrates that it is possible to develop new islet centers, thereby improving accessibility for patients.
Increased understanding of intrinsically disordered proteins (IDPs) and protein regions has revolutionized our view of the relationship between protein structure and function. Data now support that ...IDPs can be functional in the absence of a single, fixed, three-dimensional structure. Due to their dynamic morphology, IDPs have the ability to display a range of kinetics and affinity depending on what the system requires, as well as the potential for large-scale association. Although several studies have shed light on the functional properties of IDPs, the class of intrinsically disordered transcription factors (TFs) is still poorly characterized biophysically due to their combination of ordered and disordered sequences. In addition, TF modulation by small molecules has long been considered a difficult or even impossible task, limiting functional probe development. However, with evolving technology, it is becoming possible to characterize TF structure–function relationships in unprecedented detail and explore avenues not available or not considered in the past. Here we provide an introduction to the biophysical properties of intrinsically disordered TFs and we discuss recent computational and experimental efforts toward understanding the role of intrinsically disordered TFs in biology and disease. We describe a series of successful TF targeting strategies that have overcome the perception of the “undruggability” of TFs, providing new leads on drug development methodologies. Lastly, we discuss future challenges and opportunities to enhance our understanding of the structure–function relationship of intrinsically disordered TFs.
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•Proteins that contain intrinsically disordered regions have emerged as key players in numerous crucial cell functions.•Disorder offers transcription factors increased conformational flexibility and binding promiscuity.•Transcription factors that contain intrinsically disordered regions are highly abundant among disease-related proteins and present attractive therapeutic targets.•Major approaches targeting transcription factors with disordered regions include targeting aberrant pathogenic aggregates, protein–protein interactions, or targeting the DNA-binding domains.•Methodological advances in biophysical methods and their combination with molecular dynamics simulations have led the successful targeting of pathogenic disordered transcription factors.
A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with ...a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4} fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.
The plant cell wall is an important factor for determining cell shape, function and response to the environment. Secondary cell walls, such as those found in xylem, are composed of cellulose, ...hemicelluloses and lignin and account for the bulk of plant biomass. The coordination between transcriptional regulation of synthesis for each polymer is complex and vital to cell function. A regulatory hierarchy of developmental switches has been proposed, although the full complement of regulators remains unknown. Here we present a protein-DNA network between Arabidopsis thaliana transcription factors and secondary cell wall metabolic genes with gene expression regulated by a series of feed-forward loops. This model allowed us to develop and validate new hypotheses about secondary wall gene regulation under abiotic stress. Distinct stresses are able to perturb targeted genes to potentially promote functional adaptation. These interactions will serve as a foundation for understanding the regulation of a complex, integral plant component.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
15N relaxation dispersion experiments were applied to the isolated N-terminal SH3 domain of the Drosophila protein drk (drkN SH3) to study microsecond to second time scale exchange processes. The ...drkN SH3 domain exists in equilibrium between folded (F exch) and unfolded (U exch) states under nondenaturing conditions in a ratio of 2:1 at 20 °C, with an average exchange rate constant, k ex, of 2.2 s-1 (slow exchange on the NMR chemical shift time scale). Consequently a discrete set of resonances is observed for each state in NMR spectra. Within the U exch ensemble there is a contiguous stretch of residues undergoing conformational exchange on a μs/ms time scale, likely due to local, non-native hydrophobic collapse. For these residues both the F exch ↔ U exch conformational exchange process and the μs/ms exchange event within the U exch state contribute to the 15N line width and can be analyzed using CPMG-based 15N relaxation dispersion measurements. The contribution of both processes to the apparent relaxation rate can be deconvoluted numerically by combining the experimental 15N relaxation dispersion data with results from an 15N longitudinal relaxation experiment that accurately quantifies exchange rates in slow exchanging systems (Farrow, N. A.; Zhang, O.; Forman-Kay, J. D.; Kay, L. E. J. Biomol. NMR 1994, 4, 727−734). A simple, generally applicable analytical expression for the dependence of the effective transverse relaxation rate constant on the pulse spacing in CPMG experiments has been derived for a two-state exchange process in the slow exchange limit, which can be used to fit the experimental data on the global folding/unfolding transition. The results illustrate that relaxation dispersion experiments provide an extremely sensitive tool to probe conformational exchange processes in unfolded states and to obtain information on the free energy landscape of such systems.
We have previously identified peroxiredoxin-3 (PRDX-3) as a cell-surface protein that is androgen regulated in the LNCaP prostate cancer (PCa) cell line. PRDX-3 is a member of the peroxiredoxin ...family that are responsible for neutralising reactive oxygen species.
PRDX-3 expression was examined in tissue from 32 patients using immunohistochemistry. Subcellular distribution was determined using confocal microscopy. PRDX-3 expression was determined in antiandrogen-resistant cell lines by western blotting and quantitative RT-PCR. The pathways of PRDX-3 overexpression and knockdown on apoptosis and response to oxidative stress were investigated using protein arrays.
PRDX-3 is upregulated in a number of endocrine-regulated tumours; in particular in PCa and prostatic intraepithelial neoplasia. Although the majority of PRDX-3 is localised to the mitochondria, we have confirmed that PRDX-3 at the cell membrane is androgen regulated. In antiandrogen-resistant LNCaP cell lines, PRDX-3 is upregulated at the protein but not RNA level. Resistant cells also possess an upregulation of the tricarboxylic acid (TCA) pathway and resistance to H₂O₂-induced apoptosis through a failure to activate pro-apoptotic pathways. Knockdown of PRDX-3 restored H₂O₂ sensitivity.
Our results suggest that PRDX-3 has an essential role in regulating oxidation-induced apoptosis in antiandrogen-resistant cells. PRDX-3 may have potential as a therapeutic target in castrate-independent PCa.
Summary
Type IVa pili are bacterial nanomachines required for colonization of surfaces, but little is known about the organization of proteins in this system. The Pseudomonas aeruginosa pilMNOPQ ...operon encodes five key members of the transenvelope complex facilitating pilus function. While PilQ forms the outer membrane secretin pore, the functions of the inner membrane‐associated proteins PilM/N/O/P are less well defined. Structural characterization of a stable C‐terminal fragment of PilP (PilPΔ71) by NMR revealed a modified β‐sandwich fold, similar to that of Neisseria meningitidis PilP, although complementation experiments showed that the two proteins are not interchangeable likely due to divergent surface properties. PilP is an inner membrane putative lipoprotein, but mutagenesis of the putative lipobox had no effect on the localization and function of PilP. A larger fragment, PilPΔ18‐6His, co‐purified with a PilNΔ44/PilOΔ51 heterodimer as a stable complex that eluted from a size exclusion chromatography column as a single peak with a molecular weight equivalent to two heterotrimers with 1:1:1 stoichiometry. Although PilO forms both homodimers and PilN–PilO heterodimers, PilPΔ18‐6His did not interact stably with PilOΔ51 alone. Together these data demonstrate that PilN/PilO/PilP interact directly to form a stable heterotrimeric complex, explaining the dispensability of PilP's lipid anchor for localization and function.
We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured ...photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570 MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.
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