Active E. coli heteromeric acetyl-CoA carboxylase forms polymorphic helical tubular filaments.

The Escherichia coli heteromeric acetyl-CoA carboxylase (ACC) has four subunits assumed to form an elusive catalytic complex and are involved in allosteric and transcriptional regulation. The E. coli ACC represents almost all ACCs from pathogenic bacteria making it a key antibiotic development target to fight growing antibiotic resistance. Furthermore, it is a model for cyanobacterial and plant plastid ACCs as biofuel engineering targets. Here we report the catalytic E. coli ACC complex surprisingly forms tubes rather than dispersed particles. The cryo-EM structure reveals key protein-protein interactions underpinning efficient catalysis and how transcriptional regulatory roles are masked during catalysis. Discovering the protein-protein interaction interfaces that facilitate catalysis, allosteric and transcriptional regulation provides new routes to engineering catalytic activity and new targets for drug discovery.

The 2.6 Å Structure of a Tulane Virus Variant with Minor Mutations Leading to Receptor Change.

Human noroviruses (HuNoVs) are a major cause of acute gastroenteritis, contributing significantly to annual foodborne illness cases. However, studying these viruses has been challenging due to limitations in tissue culture techniques for over four decades. Tulane virus (TV) has emerged as a crucial surrogate for HuNoVs due to its close resemblance in amino acid composition and the availability of a robust cell culture system. Initially isolated from rhesus macaques in 2008, TV represents a novel Calicivirus belonging to the Recovirus genus. Its significance lies in sharing the same host cell receptor, histo-blood group antigen (HBGA), as HuNoVs. In this study, we introduce, through cryo-electron microscopy (cryo-EM), the structure of a specific TV variant (the 9-6-17 TV) that has notably lost its ability to bind to its receptor, B-type HBGA-a finding confirmed using an enzyme-linked immunosorbent assay (ELISA). These results offer a profound insight into the genetic modifications occurring in TV that are necessary for adaptation to cell culture environments. This research significantly contributes to advancing our understanding of the genetic changes that are pivotal to successful adaptation, shedding light on fundamental aspects of Calicivirus evolution.

A comparative analysis of compression bearing capacity in recycled concrete brick walls and composite walls incorporating coal-ash blocks.

In the face of the problem of waste disposal in the demolition of concrete structures, a composite wall composed of recycled concrete bricks and fly ash blocks was proposed, and based on the previous thermal performance research, its axial compression performance were further studied. Four types of walls were designed and constructed: (1) clay brick masonry (CBM), (2) recycled concrete brick masonry (RBM), (3) bilateral clay bricks masonry with coal-ash blocks sandwich insulation wall (CFCM), and (4) bilateral recycled concrete bricks masonry with coal-ash blocks sandwich insulation wall (RFRM). The test results showed that recycled concrete brick masonry exhibited a higher bearing capacity than clay brick masonry. The ultimate load of RBM was 15% higher than that of CBM. Moreover, the ultimate load of CFCM was 21% higher than that of CBM. Following the addition of sandwich coal-ash blocks in RBM, its ultimate load increased by over 42% than that of CBM. Following the addition of coal-ash blocks sandwich in both clay and recycled concrete bricks masonry, both the bearing capacity and strain exhibited improvement, the yielding load and compressive strength of them increased. Thus, it could be concluded that coal-ash blocks improved its bearing capacity. Based on the analysis of the axial compression tests, a theoretical computational model was developed and a computational expression to explain the compressive bearing capacity of a two-sided brick with coal-ash blocks sandwich insulation wall. Comparisons between the test ultimate loads (FT) and the estimated ultimate loads (FE) confirmed the accuracy of the theoretical calculation model for the compressive bearing capacity. Thus, theoretical computational models are highly recommended for the design of two-sided bricks with insulating walls constructed from coal-ash blocks being sandwiched together. This study provides a theoretical basis for the engineering application of recycled concrete brick wall and fly ash block composite wall.

"Is this blueberry ripe?": a blueberry ripeness detection algorithm for use on picking robots.

Blueberries are grown worldwide because of their high nutritional value; however, manual picking is difficult, and expert pickers are scarce. To meet the real needs of the market, picking robots that can identify the ripeness of blueberries are increasingly being used to replace manual operators. However, they struggle to accurately identify the ripeness of blueberries because of the heavy shading between the fruits and the small size of the fruit. This makes it difficult to obtain sufficient information on characteristics; and the disturbances caused by environmental changes remain unsolved. Additionally, the picking robot has limited computational power for running complex algorithms. To address these issues, we propose a new YOLO-based algorithm to detect the ripeness of blueberry fruits. The algorithm improves the structure of YOLOv5x. We replaced the fully connected layer with a one-dimensional convolution and also replaced the high-latitude convolution with a null convolution based on the structure of CBAM, and finally obtained a lightweight CBAM structure with efficient attention-guiding capability (Little-CBAM), which we embedded into MobileNetv3 while replacing the original backbone structure with the improved MobileNetv3. We expanded the original three-layer neck path by one to create a larger-scale detection layer leading from the backbone network. We added a multi-scale fusion module to the channel attention mechanism to build a multi-method feature extractor (MSSENet) and then embedded the designed channel attention module into the head network, which can significantly enhance the feature representation capability of the small target detection network and the anti-interference capability of the algorithm. Considering that these improvements will significantly extend the training time of the algorithm, we used EIOU_Loss instead of CIOU_Loss, whereas the k-means++ algorithm was used to cluster the detection frames such that the generated predefined anchor frames are better adapted to the scale of the blueberries. The algorithm in this study achieved a final mAP of 78.3% on the PC terminal, which was 9% higher than that of YOLOv5x, and the FPS was 2.1 times higher than that of YOLOv5x. By translating the algorithm into a picking robot, the algorithm in this study ran at 47 FPS and achieved real-time detection well beyond that achieved manually.

Discovery and Biological Characterization of PRMT5:MEP50 Protein-Protein Interaction Inhibitors.

Protein arginine methyltransferase 5 (PRMT5) is a master epigenetic regulator and an extensively validated therapeutic target in multiple cancers. Notably, PRMT5 is the only PRMT that requires an obligate cofactor, methylosome protein 50 (MEP50), to function. We developed compound 17, a novel small-molecule PRMT5:MEP50 protein-protein interaction (PPI) inhibitor, after initial virtual screen hit identification and analogue refinement. Molecular docking indicated that compound 17 targets PRMT5:MEP50 PPI by displacing the MEP50 W54 burial into a hydrophobic pocket of the PRMT5 TIM barrel. In vitro analysis indicates IC50 < 500 nM for prostate and lung cancer cells with selective, specific inhibition of PRMT5:MEP50 substrate methylation and target gene expression, and RNA-seq analysis suggests that compound 17 may dysregulate TGF-ß signaling. Compound 17 provides a proof of concept in targeting PRMT5:MEP50 PPI, as opposed to catalytic targeting, as a novel mechanism of action and supports further preclinical development of inhibitors in this class.

Spatial and Temporal Variations of Polar Ionospheric Total Electron Content over Nearly Thirteen Years.

It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the Weddell Sea anomaly (WSA) as well as geomagnetic storms. In this paper, four different models are utilized to map the ionospheric TEC over the Arctic and Antarctic for about one solar cycle: the polynomial (POLY) model, the generalized trigonometric series function (GTSF) model, the spherical harmonic (SH) model, and the spherical cap harmonic (SCH) model. Compared to other models, the SCH model has the best performance with ±0.8 TECU of residual mean value and 1.5-3.5 TECU of root mean square error. The spatiotemporal distributions and variations of the polar ionospheric TEC are investigated and compared under different ionosphere conditions in the Arctic and Antarctic. The results show that the solar activity significantly affects the TEC variations. During polar days, the ionospheric TEC is more active than it is during polar nights. In polar days over the Antarctic, the maximum value of TEC always appears at night in the Antarctic Peninsula and Weddell Sea area affected by the WSA. In the same year, the ionospheric TEC of the Antarctic has a larger amplitude of annual variation than that of the TEC in the Arctic. In addition, the evolution of the ionization patch during a geomagnetic storm over the Antarctic can be clearly tracked employing the SCH model, which appears to be adequate for mapping the polar TEC, and provides a sound basis for further automatic identification of ionization patches.

Study on the Quality Control for Periodogram in the Determination of Water Level Using the GNSS-IR Technique.

A GNSS station, located on the shore of sea and inland waters, and equipped with standard geodetic receivers and antennas, can be used to measure water levels using a technique called GNSS Interferometric Reflectometry (GNSS-IR). The classical GNSS-IR method is based on SNR data and LSP spectrum analysis method. In order to promote the application of GNSS-IR, the accuracy of the results needs to be further improved, and quality control needs to be achieved better. Classical quality control methods include denoising filtering based on data source SNR; post-processing filtering based on results; morphological analysis based on parameters, such as the ratio of the maximum peak value to the background noise mean, the ratio of the maximum peak to the sub-peak, and the amplitude of the maximum peak. All three methods have the problem of correct frequency extraction under multiple approximate peak conditions. This paper focuses on the performance analysis of three methods of quality control for two situations with real examples, summarizes the advantages and disadvantages of each method, and discusses the measures in applications. Considering the limitations in the threshold setting for the third method, a new quality control method combining multiple parameters and external constraints is proposed. This method is more flexible, especially in dealing with a periodogram with multiple similar peaks, breaking through the premise that the frequency corresponding to the maximum peak is the correct frequency, and validated in two different environments. The experimental results show that the proposed method can improve the accuracy of the measured water level while ensuring the amount of the results. It eliminates the gross errors effectively and uses the data efficiently.

Structural basis for reactivating the mutant TERT promoter by cooperative binding of p52 and ETS1.

Transcriptional factors ETS1/2 and p52 synergize downstream of non-canonical NF-κB signaling to drive reactivation of the -146C>T mutant TERT promoter in multiple cancer types, but the mechanism underlying this cooperativity remains unknown. Here we report the crystal structure of a ternary p52/ETS1/-146C>T TERT promoter complex. While p52 needs to associate with consensus κB sites on the DNA to function during non-canonical NF-κB signaling, we show that p52 can activate the -146C>T TERT promoter without binding DNA. Instead, p52 interacts with ETS1 to form a heterotetramer, counteracting autoinhibition of ETS1. Analogous to observations with the GABPA/GABPB heterotetramer, the native flanking ETS motifs are required for sustained activation of the -146C>T TERT promoter by the p52/ETS1 heterotetramer. These observations provide a unifying mechanism for transcriptional activation by GABP and ETS1, and suggest that genome-wide targets of non-canonical NF-κB signaling are not limited to those driven by consensus κB sequences.

Structural and mechanistic insights into NDM-1 catalyzed hydrolysis of cephalosporins.

Cephalosporins constitute a large class of ß-lactam antibiotics clinically used as antimicrobial drugs. New Dehli metallo-ß-lactamase (NDM-1) poses a global threat to human health as it confers on bacterial pathogen resistance to almost all ß-lactams, including penicillins, cephalosporins, and carbapenems. Here we report the first crystal structures of NDM-1 in complex with cefuroxime and cephalexin, as well as NMR spectra monitoring cefuroxime and cefixime hydrolysis catalyzed by NDM-1. Surprisingly, cephalosporoate intermediates were captured in both crystal structures determined at 1.3 and 2.0 Å. These results provide detailed information concerning the mechanism and pathways of cephalosporin hydrolysis. We also present the crystal structure and enzyme assays of a D124N mutant, which reveals that D124 most likely plays a more structural than catalytic role.

Structural basis for the unique heterodimeric assembly between cerebral cavernous malformation 3 and germinal center kinase III.

Defects in cerebral cavernous malformation protein CCM3 result in cerebral cavernous malformation (CCM), a common vascular lesion of the human CNS. CCM3 functions as an adaptor protein that interacts with various signal proteins. Among these partner proteins, germinal center kinase III (GCKIII) proteins have attracted significant interest because GCKIII-CCM3 interactions play essential roles in vascular physiology. Here, we report the crystal structures of CCM3 in complex with the C-terminal regulatory domains of GCKIII (GCKIIIct) at 2.4 Å resolution. Our results reveal that GCKIIIct adopts a fold closely resembling that of the CCM3 N-terminal dimeric domain. GCKIIIct heterodimerizes with CCM3 in a manner analogous to CCM3 homodimerization. The remarkable structural rearrangement of CCM3 induced by GCKIIIct binding and the ensuing interactions within CCM3 are characterized as the structural determinants for GCKIIIct-CCM3 heterodimerization. Taken together, these findings provide a precise structural basis for GCKIIIct-CCM3 heterodimerization and the functional performance of GCKIII mediated by CCM3.

Crystallization and preliminary crystallographic studies of CCM3 in complex with the C-terminal domain of MST4.

MST4 is a member of the GCKIII kinases. The interaction between cerebral cavernous malformation 3 (CCM3) and GCKIII kinases plays a critical role in cardiovascular development and in cerebral cavernous malformations. The complex of CCM3 and the C-terminal domain of MST4 has been constructed, purified and crystallized, and a diffraction data set has been collected to 2.4 Šresolution. The crystal of the CCM3-MST4 C-terminal domain complex belonged to space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = 69.10, b = 69.10, c = 117.57 Å.