Explore the vast range of titles available.

The coronavirus membrane protein (M) is the most abundant viral structural protein and plays a central role in virus assembly and morphogenesis. However, the process of M protein-driven virus assembly are largely unknown. Here, we report the cryo-electron microscopy structure of the SARS-CoV-2 M protein in two different conformations. M protein forms a mushroom-shaped dimer, composed of two transmembrane domain-swapped three-helix bundles and two intravirion domains. M protein further assembles into higher-order oligomers. A highly conserved hinge region is key for conformational changes. The M protein dimer is unexpectedly similar to SARS-CoV-2 ORF3a, a viral ion channel. Moreover, the interaction analyses of M protein with nucleocapsid protein (N) and RNA suggest that the M protein mediates the concerted recruitment of these components through the positively charged intravirion domain. Our data shed light on the M protein-driven virus assembly mechanism and provide a structural basis for therapeutic intervention targeting M protein. M protein plays essential roles in virus assembly and morphogenesis. Here, authors reveal two cryo-EM structures of M protein from SARS-CoV-2 that suggest conformational dynamics of M protein and its role in virus assembly.

Trehalose-6-phosphate synthase (TPS) is an essential enzyme for synthesizing trehalose and is a significant regulator of plant development and stress response. Sweet orange ( ) is an economically important fruit tree crop and a common transgenic material. At present, little information is available about the gene family in sweet orange. The gene family were identified from sweet orange genome by bioinformatics analysis. Additionally, the expression of genes was analyzed under phytohormones and abiotic stresses by quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR). Here, eight genes were identified and were found to be randomly distributed in five sweet orange chromosomes. TPS and trehalose-6-phosphate phosphatase (TPP) domains were observed in all CisTPS proteins. The phylogenetic tree showed that genes were divided into two subfamilies, and genes in each subfamily had conserved intron structures and motif compositions. The -acting elements of genes suggested their roles in phytohormone and stress responses. All genes were ubiquitously expressed in roots, leaves, and stems, and six members were highly expressed in roots. Expression profiles showed that genes exhibited tissue specificity and were differentially expressed in response to phytohormones and abiotic stresses. This study lays a foundation for revealing the functions of the gene family in trehalose regulation in sweet orange, and provides a valuable reference for this gene family in other plants.

Tetraspanins play critical roles in various physiological processes, ranging from cell adhesion to virus infection. The members of the tetraspanin family have four membrane-spanning domains and short and large extracellular loops, and associate with a broad range of other functional proteins to exert cellular functions. Here we report the crystal structure of CD9 and the cryo-electron microscopic structure of CD9 in complex with its single membrane-spanning partner protein, EWI-2. The reversed cone-like molecular shape of CD9 generates membrane curvature in the crystalline lipid layers, which explains the CD9 localization in regions with high membrane curvature and its implications in membrane remodeling. The molecular interaction between CD9 and EWI-2 is mainly mediated through the small residues in the transmembrane region and protein/lipid interactions, whereas the fertilization assay revealed the critical involvement of the LEL region in the sperm-egg fusion, indicating the different dependency of each binding domain for other partner proteins. Tetraspanins play critical roles in various physiological processes, ranging from cell adhesion to virus infection. Here authors report the crystal structure of CD9 and the cryo-electron microscopic structure of CD9 in complex with its single membrane-spanning partner protein, EWI-2.

Chronic infection with hepatitis B virus (HBV) affects more than 290 million people worldwide, is a major cause of cirrhosis and hepatocellular carcinoma, and results in an estimated 820,000 deaths annually 1 , 2 . For HBV infection to be established, a molecular interaction is required between the large glycoproteins of the virus envelope (known as LHBs) and the host entry receptor sodium taurocholate co-transporting polypeptide (NTCP), a sodium-dependent bile acid transporter from the blood to hepatocytes 3 . However, the molecular basis for the virus–transporter interaction is poorly understood. Here we report the cryo-electron microscopy structures of human, bovine and rat NTCPs in the apo state, which reveal the presence of a tunnel across the membrane and a possible transport route for the substrate. Moreover, the cryo-electron microscopy structure of human NTCP in the presence of the myristoylated preS1 domain of LHBs, together with mutation and transport assays, suggest a binding mode in which preS1 and the substrate compete for the extracellular opening of the tunnel in NTCP. Our preS1 domain interaction analysis enables a mechanistic interpretation of naturally occurring HBV-insusceptible mutations in human NTCP. Together, our findings provide a structural framework for HBV recognition and a mechanistic understanding of sodium-dependent bile acid translocation by mammalian NTCPs. Cryo-electron microscopy structures of the bile acid transporter NTCP in the apo state and in complex with the preS1 domain of hepatitis B virus (HBV) provide insight into NTCP substrate transport and HBV recognition mechanisms.

Hepatitis B virus (HBV), a leading cause of developing hepatocellular carcinoma affecting more than 290 million people worldwide, is an enveloped DNA virus specifically infecting hepatocytes. Myristoylated preS1 domain of the HBV large surface protein binds to the host receptor sodium-taurocholate cotransporting polypeptide (NTCP), a hepatocellular bile acid transporter, to initiate viral entry. Here, we report the cryogenic-electron microscopy structure of the myristoylated preS1 (residues 2–48) peptide bound to human NTCP. The unexpectedly folded N-terminal half of the peptide embeds deeply into the outward-facing tunnel of NTCP, whereas the C-terminal half formed extensive contacts on the extracellular surface. Our findings reveal an unprecedented induced-fit mechanism for establishing high-affinity virus–host attachment and provide a blueprint for the rational design of anti-HBV drugs targeting virus entry. In this study, Asami et al. present the cryo-EM structure of the complex between hepatitis B virus protein and its host entry receptor NTCP, which provide a blueprint for the rational design of anti-HBV drugs targeting virus entry.

Zinc ions (Zn 2+ ) are vital to most cells, with the intracellular concentrations of Zn 2+ being tightly regulated by multiple zinc transporters located at the plasma and organelle membranes. We herein present the 2.2-3.1 Å-resolution cryo-EM structures of a Golgi-localized human Zn 2+ /H + antiporter ZnT7 (hZnT7) in Zn 2+ -bound and unbound forms. Cryo-EM analyses show that hZnT7 exists as a dimer via tight interactions in both the cytosolic and transmembrane (TM) domains of two protomers, each of which contains a single Zn 2+ -binding site in its TM domain. hZnT7 undergoes a TM-helix rearrangement to create a negatively charged cytosolic cavity for Zn 2+ entry in the inward-facing conformation and widens the luminal cavity for Zn 2+ release in the outward-facing conformation. An exceptionally long cytosolic histidine-rich loop characteristic of hZnT7 binds two Zn 2+ ions, seemingly facilitating Zn 2+ recruitment to the TM metal transport pathway. These structures permit mechanisms of hZnT7-mediated Zn 2+ uptake into the Golgi to be proposed. ZnT7 is a Golgi-localized Zn2 + /H+ antiporter. Here the authors present the cryo-EM structures of human ZnT7 in Zn2 + -bound and unbound forms, shedding light on its mechanism of Zn2+ transport.

Objective This study aims to analyze the clinical features and genetic mutation characteristics of a family with Dentinogenesis Imperfecta Shields type II (DGI-II) and to observe the behavior of the stem cells from human exfoliated deciduous teeth (SHED) to explore the relationship between the locus of dentin sialophosphoprotein ( DSPP ) mutations and family clinical manifestations. Materials and methods After collecting clinical data from the family, Whole Genome Sequencing (WGS) followed by Sanger sequencing was used to identify pathogenic genes sites. The physical characteristics of the patient’s teeth were examined using Micro-CT, scanning electron microscopy (SEM), and microhardness analysis. The behavior of SHEDs was studied through flow cytometry, adipogenic and osteogenic differentiation, quantitative real-time PCR (qRT-PCR), Western blotting, CCK-8 proliferation assays, colony formation, and cell migration experiments. Results A novel frameshift mutation, DSPP c.2695delA.N899fs, was identified in the family. Micro-CT showed significant wear in the patient’s teeth. SEM results revealed reduced and irregular dentinal tubules. Microhardness analysis showed significantly lower hardness in the patient’s teeth. CCK-8, colony formation, and migration assays demonstrated reduced proliferation and migration capacities in the patient’s SHEDs. qRT-PCR and Western blot results showed lower expression of DSPP , RUNX2 , OCN , and ALP compared to controls, but higher DSPP protein level in the patient’s SHEDs. Osteogenic differentiation tests indicated reduced mineralization capacity of the patient’s SHEDs. Conclusion This study identified a novel frameshift mutation, DSPP c.2695delA.N899fs, in a DGI-II family and demonstrated its impact on SHED proliferation, migration, and mineralization. The findings demonstrated that this novel variant disturbs dentinal characteristics and cell behavior of SHED. Significance This study provides insights into the genetic and cellular basis of DGI-II, elucidating the role of a novel DSPP mutation in tooth structure development and stem cell behavior. However, in vivo validation of this DSPP mutation is important to further confirm this conclusion.

Multidrug resistance (MDR) poses a major challenge to medicine. A principle cause of MDR is through active efflux by MDR transporters situated in the bacterial membrane. Here we present the crystal structure of the major facilitator superfamily (MFS) drug/H + antiporter MdfA from Escherichia coli in an outward open conformation. Comparison with the inward facing (drug binding) state shows that, in addition to the expected change in relative orientations of the N- and C-terminal lobes of the antiporter, the conformation of TM5 is kinked and twisted. In vitro reconstitution experiments demonstrate the importance of selected residues for transport and molecular dynamics simulations are used to gain insights into antiporter switching. With the availability of structures of alternative conformational states, we anticipate that MdfA will serve as a model system for understanding drug efflux in MFS MDR antiporters. The multidrug resistance transporter mediated efflux of antibiotics from the bacterial cytoplasm represents a major challenge to medicine. Here authors solve the X-ray crystallographic structure of the drug/H+ antiporter MdfA from Escherichia coli and shed light on the conformational switching mechanism.

Alcohol exposure induces kidney oxidative stress and inflammatory responses. L‐theanine (LTA) can protect the kidneys through its antioxidant and immunomodulatory effects; however, its role and underlying mechanisms in alleviating alcoholic kidney injury remain unclear. In this study, LTA significantly ameliorated alcohol‐induced kidney tissue structural damage, excessive release of inflammatory factors, and oxidative stress imbalance, with the 400 mg kg −1 day −1 dose group showing the most effective intervention. LTA inhibited the sphingolipid metabolism‐S1PR2‐JNK signaling pathway, reduced sphingosine levels, downregulated the S1PR2 proinflammatory receptor, blocked S1PR2 signal transduction, and subsequently suppressed JNK phosphorylation and AP‐1 activity. Additionally, LTA activated the PPARα and steroid synthesis pathway, promoting the production of endogenous anti‐inflammatory steroids. These results indicate that LTA alleviates alcohol‐induced kidney injury by inhibiting the sphingolipid metabolism‐S1PR2‐JNK pathway and activating the PPARα and steroid synthesis pathways, providing a safe and effective nutritional intervention strategy for alcoholic kidney injury.

MgtE is a Mg 2+ channel conserved in organisms ranging from prokaryotes to eukaryotes, including humans, and plays an important role in Mg 2+ homeostasis. The previously determined MgtE structures in the Mg 2+ -bound, closed-state, and structure-based functional analyses of MgtE revealed that the binding of Mg 2+ ions to the MgtE cytoplasmic domain induces channel inactivation to maintain Mg 2+ homeostasis. There are no structures of the transmembrane (TM) domain for MgtE in Mg 2+ -free conditions, and the pore-opening mechanism has thus remained unclear. Here, we determined the cryo-electron microscopy (cryo-EM) structure of the MgtE-Fab complex in the absence of Mg 2+ ions. The Mg 2+ -free MgtE TM domain structure and its comparison with the Mg 2+ -bound, closed-state structure, together with functional analyses, showed the Mg 2+ -dependent pore opening of MgtE on the cytoplasmic side and revealed the kink motions of the TM2 and TM5 helices at the glycine residues, which are important for channel activity. Overall, our work provides structure-based mechanistic insights into the channel gating of MgtE.