An interdomain hydrogen bond in the Rag GTPases maintains stable mTORC1 signaling in sensing amino acids

Cellular growth and proliferation are primarily dictated by the mechanistic target of rapamycin complex 1 (mTORC1), which balances nutrient availability against the cell\u27s anabolic needs. Central to the activity of mTORC1 is the RagA-RagC GTPase heterodimer, which under favorable conditions recruits the complex to the lysosomal surface to promote its activity. The RagA-RagC heterodimer has a unique architecture in that both subunits are active GTPases. To promote mTORC1 activity, the RagA subunit is loaded with GTP and the RagC subunit is loaded with GDP, while the opposite nucleotide-loading configuration inhibits this signaling pathway. Despite its unique molecular architecture, how the Rag GTPase heterodimer maintains the oppositely loaded nucleotide state remains elusive. Here, we applied structure-function analysis approach to the crystal structures of the Rag GTPase heterodimer and identified a key hydrogen bond that stabilizes the GDP-loaded state of the Rag GTPases. This hydrogen bond is mediated by the backbone carbonyl of Asn30 in the nucleotide-binding domain of RagA or Lys84 of RagC and the hydroxyl group on the side chain of Thr210 in the C-terminal roadblock domain of RagA or Ser266 of RagC, respectively. Eliminating this interdomain hydrogen bond abolishes the ability of the Rag GTPase to maintain its functional state, resulting in a distorted response to amino acid signals. Our results reveal that this long-distance interdomain interaction within the Rag GTPase is required for the maintenance and regulation of the mTORC1 nutrient-sensing pathway

Haematopinus Infestations and Mycoplasma Infections of Water Buffalo (Bubalus bubalis) Herds in National Parks of Hungary

The biology, epidemiology and pathology of sucking louse infestation and Mycoplasma infection of water buffalo (Bubalus bubalis) herds in Hungarian national parks were studied between 19 December 2011 and 4 May 2012. A total of 333 water buffaloes were examined in buffalo stocks of the Balaton Uplands, Fertő-Hanság and Kiskunság National Parks. The objective was to determine the prevalence and rate of sucking louse infestation and mycoplasma infection among water buffaloes. Always an area of identical size (2 cm2) was examined on the right or left side of the middle part of the animals' neck. A total of 3106 eggs, 10 nymphs and 105 adults of the sucking louse Haematopinus tuberculatus were identified with the help of a Conrad USB microscopic camera and a Wild-Leitz-Leica M420 photomacroscope. The data were evaluated using the Quantitative Parasitology software QP 3.0. The prevalence of mycoplasmas was determined in 20 randomly selected buffaloes of two national parks with the help of sterile nasal and vaginal transport swabs (Sarstedt). All of the 10 nasal swabs collected from buffaloes in the Balaton Uplands National Park contained Mycoplasma bovirhinis and three swab samples yielded M. bovis as well. Mycoplasma bovirhinis was cultured from 8 out of 10 swabs taken from the vagina, and three vaginal samples also yielded M. bovis. Similar results were obtained by testing samples collected from buffaloes in the Kiskunság National Park (Mórahalom). All ten nasal swab samples yielded M. bovirhinis. From two samples a mixture of M. bovirhinis and M. bovis was cultured. Nine out of the 10 vaginal swabs yielded M. bovirhinis while two showed a combined infection by M. bovis and M. bovirhinis

Termi-Luc: a versatile assay to monitor full-protein release from ribosomes

Termination of protein biosynthesis is an essential step of gene expression, during which a complete functional protein is released from the ribosome. Premature or inefficient termination results in truncated, non-functional or toxic proteins that may cause disease. Indeed, more than 10% of human genetic diseases are caused by nonsense mutations leading to premature termination. Efficient and sensitive approaches are required to study eukaryotic termination mechanisms and to identify potential therapeutics that modulate termination. Canonical radioactivity-based termination assays are complex, report on a short peptide release, and are incompatible with high-throughput screening. Here we describe a robust and simple in vitro assay to study the kinetics of full-protein release. The assay monitors luminescence upon release of nanoluciferase from a mammalian pre-termination complex. The assay can be used to record time-progress curves of protein release in a high-throughput format, making it optimal for studying release kinetics and for high-throughput screening for small molecules that modulate the efficiency of termination

Multi-mass solvers for lattice QCD on GPUs

Graphical Processing Units (GPUs) are more and more frequently used for lattice QCD calculations. Lattice studies often require computing the quark propagators for several masses. These systems can be solved using multi-shift inverters but these algorithms are memory intensive which limits the size of the problem that can be solved using GPUs. In this paper, we show how to efficiently use a memory-lean single-mass inverter to solve multi-mass problems. We focus on the BiCGstab algorithm for Wilson fermions and show that the single-mass inverter not only requires less memory but also outperforms the multi-shift variant by a factor of two.Comment: 27 pages, 6 figures, 3 Table

Absorption and wavepackets in optically excited semiconductor superlattices driven by dc-ac fields

Within the one-dimensional tight-binding minibands and on-site Coloumbic interaction approximation, the absorption spectrum and coherent wavepacket time evolution in an optically excited semiconductor superlattice driven by dc-ac electric fields are investigated using the semiconductor Bloch equations. The dominating roles of the ratios of dc-Stark to external ac frequency, as well as ac-Stark to external ac frequency, is emphasized. If the former is an integer ${\cal N}$, then also ${\cal N}$ harmonics are present within one Stark frequency, while the fractional case leads to the formation of excitonic fractional ladders. The later ratio determines the size and profile of the wavepacket. In the absence of excitonic interaction it controls the maximum size wavepackets reach within one cycle, while the interaction produces a strong anisotropy and tends to palliate the dynamic wavepacket localization.Comment: 14 pages, 7 postscript figure

Relation to intramuscular connective tissue properties to CT-values in longissimus thoracis muscle of Hungarian simmental cattle

Intramuscular connective tissue plays an important role in determining meat tenderness. The objective of the research was to compare the collagen/hydroxyproline content and X-ray Computed Tomographic (CT) connective tissue proportion of longissimus thoracis (LT) muscle in Hungarian Simmental bulls and cows. Animals (n=24) were slaughtered at similar live weight (bulls: 530.6+44.7 kg, cows: 527.3+53.5 kg) under standard commercial conditions in Hungary. After 24 h chilling, LT samples were taken from the right half carcass at the 12th rib. CT examinations were carried out with a 16-slice CT system (slice thickness: 5 mm). Samples were scanned at different user-selectable tube voltages e.g. low: 80 kV and high: 140 kV. CT value at LT muscle area of each mixed scan (80 and 140 kV) was determined. Volumetric connective tissue content was measured (above 200 CT value) as well. Following CT, the hydroxyproline/collagen content and intramuscular fat content of LT were determined. Cows had lower carcass weight (247 kg vs 295 kg), EU conformation score (3.5 vs 5.5), and fatness score (4.2 vs 5.9) than bulls (P<0.01). Bulls had higher LT area, but intramuscular fat content was similar for bulls (2.8±1.9) and cows (2.7±2.0). On the other hand, bulls had lower CT intramuscular connective tissue proportion in LT compared to cows (0.4±0.2% vs 0.7±0.3% P<0.01). The same tendency could be observed for the collagen content (0.5±0.2% vs 0.7±0.1% P<0.01). Correlation between the CT connective tissue proportion of LT and collagen content was r=0.8 (P=0.000). There was a weak positive correlation between slaughter age and CT connective tissue as well as collagen content of LT (r=0.3–0.4, P<0.05). In conclusion, intramuscular connective tissue proportion in LT increased with slaughter age, and older cows had higher collagen and connective tissue proportion than bulls. Mixed CT scans can be used for the analysis of intramuscular connective tissue content

SARS-CoV-2 Spike protein variant D614G increases infectivity and retains sensitivity to antibodies that target the receptor binding domain [preprint]

Virus genome sequence variants that appear over the course of an outbreak can be exploited to map the trajectory of the virus from one susceptible host to another. While such variants are usually of no functional significance, in some cases they may allow the virus to transmit faster, change disease severity, or confer resistance to antiviral therapies. Since the discovery of SARS-CoV-2 as the cause of COVID-19, the virus has spread around the globe, and thousands of SARS-CoV-2 genomes have been sequenced. The rate of sequence variation among SARS-CoV-2 isolates is modest for an RNA virus but the enormous number of human-to-human transmission events has provided abundant opportunity for selection of sequence variants. Among these, the SARS-CoV-2 Spike protein variant, D614G, was not present in the presumptive common ancestor of this zoonotic virus, but was first detected in late January in Germany and China. The D614G variant steadily increased in frequency and now constitutes \u3e97% of isolates world-wide, raising the question whether D614G confers a replication advantage to SARS-CoV-2. Structural models predict that D614G would disrupt contacts between the S1 and S2 domains of the Spike protein and cause significant shifts in conformation. Using single-cycle vectors we showed that D614G is three to nine-fold more infectious than the ancestral form on human lung and colon cell lines, as well as on other human cell lines rendered permissive by ectopic expression of human ACE2 and TMPRSS2, or by ACE2 orthologues from pangolin, pig, dog, or cat. Nonetheless, monoclonal antibodies targeting the receptor binding domain of the SARS-CoV-2 Spike protein retain full neutralization potency. These results suggest that D614G was selected for increased human-to-human transmission, that it contributed to the rapidity of SARS-CoV-2 spread around the world, and that it does not confer resistance to antiviral therapies targeting the receptor binding domain

Diagrammatic Quantum Monte Carlo for Two-Body Problem: Exciton

We present a novel method for precise numerical solution of the irreducible two-body problem and apply it to excitons in solids. The approach is based on the Monte Carlo simulation of the two-body Green function specified by Feynman's diagrammatic expansion. Our method does not rely on the specific form of the electron and hole dispersion laws and is valid for any attractive electron-hole potential. We establish limits of validity of the Wannier (large radius) and Frenkel (small radius) approximations, present accurate data for the intermediate radius excitons, and give evidence for the charge transfer nature of the monopolar exciton in mixed valence materials.Comment: 4 pages, 5 figure

Human longevity is characterised by high thyroid stimulating hormone secretion without altered energy metabolism

Neuro Imaging Researc