Scaffolded DNA origami is a versatile means of synthesizing complex molecular architectures. However, the approach is limited by the need to forward-design specific Watson-Crick base pairing manually ...for any given target structure. Here, we report a general, top-down strategy to design nearly arbitrary DNA architectures autonomously based only on target shape. Objects are represented as closed surfaces rendered as polyhedral networks of parallel DNA duplexes, which enables complete DNA scaffold routing with a spanning tree algorithm. The asymmetric polymerase chain reaction is applied to produce stable, monodisperse assemblies with custom scaffold length and sequence that are verified structurally in three dimensions to be high fidelity by single-particle cryo-electron microscopy. Their long-term stability in serum and low-salt buffer confirms their utility for biological as well as nonbiological applications.
MuB is a non-specific DNA-binding protein and AAA+ ATPase that significantly influences the DNA transposition process of bacteriophage Mu, especially in target DNA selection for transposition. While ...studies have established the ATP-dependent formation of MuB filament as pivotal to this process, the high-resolution structure of a full-length MuB protomer and the underlying molecular mechanisms governing its oligomerization remain elusive. Here, we use cryo-EM to obtain a 3.4-Å resolution structure of the ATP(+)-DNA(+)-MuB helical filament, which encapsulates the DNA substrate within its axial channel. The structure categorizes MuB within the initiator clade of the AAA+ protein family and precisely locates the ATP and DNA binding sites. Further investigation into the oligomeric states of MuB show the existence of various forms of the filament. These findings lead to a mechanistic model where MuB forms opposite helical filaments along the DNA, exposing potential target sites on the bare DNA and then recruiting MuA, which stimulates MuB’s ATPase activity and disrupts the previously formed helical structure. When this happens, MuB generates larger ring structures and dissociates from the DNA.Here, Zhao et al. use cryo-EM to show how MuB forms helical filaments around DNA. These structures play a crucial role in target DNA selection and transposition, shedding light on MuB’s functional mechanism.
Psoriasis is a chronic inflammatory skin disease. The histopathological features of psoriasis include excessive proliferation of keratinocytes and infiltration of immune cells. The S100 proteins are ...a group of EF-hand Ca
-binding proteins, including S100A2, -A7, -A8/A9, -A12, -A15, which expression levels are markedly upregulated in psoriatic skin. These proteins exert numerous functions such as serving as intracellular Ca
sensors, transduction of Ca
signaling, response to extracellular stimuli, energy metabolism, and regulating cell proliferation and apoptosis. Evidence shows a crucial role of S100 proteins in the development and progress of inflammatory diseases, including psoriasis. S100 proteins can possibly be used as potential therapeutic target and diagnostic biomarkers. This review focuses on the pathogenic role of S100 proteins in psoriasis.
Specimens below 50 kDa have generally been considered too small to be analyzed by single-particle cryo-electron microscopy (cryo-EM). The high flexibility of pure RNAs makes it difficult to obtain ...high-resolution structures by cryo-EM. In bacteria, riboswitches regulate sulfur metabolism through binding to the S-adenosylmethionine (SAM) ligand and offer compelling targets for new antibiotics. SAM-I, SAM-I/IV, and SAM-IV are the three most commonly found SAM riboswitches, but the structure of SAM-IV is still unknown. Here, we report the structures of apo and SAM-bound SAM-IV riboswitches (119-nt, ~40 kDa) to 3.7 Å and 4.1 Å resolution, respectively, using cryo-EM. The structures illustrate homologies in the ligand-binding core but distinct peripheral tertiary contacts in SAM-IV compared to SAM-I and SAM-I/IV. Our results demonstrate the feasibility of resolving small RNAs with enough detail to enable detection of their ligand-binding pockets and suggest that cryo-EM could play a role in structure-assisted drug design for RNA.
Group I introns are catalytic RNAs that coordinate two consecutive transesterification reactions for self-splicing. To understand how the group I intron promotes catalysis and coordinates ...self-splicing reactions, we determine the structures of L-16 Tetrahymena ribozyme in complex with a 5'-splice site analog product and a 3'-splice site analog substrate using cryo-EM. We solve six conformations from a single specimen, corresponding to different splicing intermediates after the first ester-transfer reaction. The structures reveal dynamics during self-splicing, including large conformational changes of the internal guide sequence and the J5/4 junction as well as subtle rearrangements of active-site metals and the hydrogen bond formed between the 2'-OH group of A261 and the N2 group of guanosine substrate. These results help complete a detailed structural and mechanistic view of this paradigmatic group I intron undergoing the second step of self-splicing.
Developing X-ray scintillators that are water-dispersible, compatible with polymeric matrices, and processable to flexible substrates is an important challenge. Herein, Tb
-doped Na
Lu
F
is ...introduced as an X-ray scintillating material with steady-state X-ray light yields of 15,800 photons MeV
, which is generated as nanocrystals on halloysite nanotubes. The obtained product exhibits good water-dispersibility and highly sensitive luminescence to X-rays. It is deposited onto a polyurethane foam to afford a composite foam material with dose-dependent radioluminescence. Moreover, the product is dispersed into polymer matrixes in aqueous solution to prepare rigid or flexible scintillator screen for X-ray imaging. As a third example, it is incorporated multilayer hydrogels for information camouflage and multilevel encryption. Encrypted information can be recognized only by X-ray irradiation, while the false information is read out under UV light. Altogether, we demonstrate that the water-dispersible scintillators are highly promising for aqueous processing of radioluminescent, X-ray imaging, and information encrypting materials.
Paclitaxel is widely used in cancer treatments, but poor water-solubility and toxicity raise serious concerns. Here we report an RNA four-way junction nanoparticle with ultra-thermodynamic stability ...to solubilize and load paclitaxel for targeted cancer therapy. Each RNA nanoparticle covalently loads twenty-four paclitaxel molecules as a prodrug. The RNA-paclitaxel complex is structurally rigid and stable, demonstrated by the sub-nanometer resolution imaging of cryo-EM. Using RNA nanoparticles as carriers increases the water-solubility of paclitaxel by 32,000-fold. Intravenous injections of RNA-paclitaxel nanoparticles with specific cancer-targeting ligand dramatically inhibit breast cancer growth, with nearly undetectable toxicity and immune responses in mice. No fatalities are observed at a paclitaxel dose equal to the reported LD
. The use of ultra-thermostable RNA nanoparticles to deliver chemical prodrugs addresses issues with RNA unfolding and nanoparticle dissociation after high-density drug loading. This finding provides a stable nano-platform for chemo-drug delivery as well as an efficient method to solubilize hydrophobic drugs.
Vitamin C (L-ascorbic acid) is an essential nutrient for human health, and its deficiency has long been known to cause scurvy. Sodium-dependent vitamin C transporters (SVCTs) are responsible for ...vitamin C uptake and tissue distribution in mammals. Here, we present cryogenic electron microscopy structures of mouse SVCT1 in both the apo and substrate-bound states. Mouse SVCT1 forms a homodimer with each protomer containing a core domain and a gate domain. The tightly packed extracellular interfaces between the core domain and gate domain stabilize the protein in an inward-open conformation for both the apo and substrate-bound structures. Vitamin C binds at the core domain of each subunit, and two potential sodium ions are identified near the binding site. The coordination of sodium ions by vitamin C explains their coupling transport. SVCTs probably deliver substrate through an elevator mechanism in combination with local structural arrangements. Altogether, our results reveal the molecular mechanism by which SVCTs recognize vitamin C and lay a foundation for further mechanistic studies on SVCT substrate transport.
Assembly-line polyketide synthases, such as the 6-deoxyerythronolide B synthase (DEBS), are large enzyme factories prized for their ability to produce specific and complex polyketide products. By ...channeling protein-tethered substrates across multiple active sites in a defined linear sequence, these enzymes facilitate programmed small-molecule syntheses that could theoretically be harnessed to access countless polyketide product structures. Using cryogenic electron microscopy to study DEBS module 1, we present a structural model describing this substrate-channeling phenomenon. Our 3.2- to 4.3-angstrom-resolution structures of the intact module reveal key domain-domain interfaces and highlight an unexpected module asymmetry. We also present the structure of a product-bound module that shines light on a recently described “turnstile” mechanism for transient gating of active sites along the assembly line.
Psoriasis is a prevalent skin disease affecting approximately 1%-3% of the population and imposes significant medical, social and economic burdens. Psoriasis involves multiple organs and is often ...complicated with obesity, diabetes, dyslipidemia, and hypertension. Because of the benefits of lipid-lowering agents and antidiabetic medications for psoriasis, metabolic abnormalities possibly play a pathogenic role in psoriasis.Psoriasis is a prevalent skin disease affecting approximately 1%-3% of the population and imposes significant medical, social and economic burdens. Psoriasis involves multiple organs and is often complicated with obesity, diabetes, dyslipidemia, and hypertension. Because of the benefits of lipid-lowering agents and antidiabetic medications for psoriasis, metabolic abnormalities possibly play a pathogenic role in psoriasis.This review focuses on the impacts of a variety of metabolic disorders on psoriasis and the underlying mechanisms.This review focuses on the impacts of a variety of metabolic disorders on psoriasis and the underlying mechanisms.In psoriasis, enhanced glycolysis, glutamine metabolism and altered fatty acid composition in the psoriatic lesion and plasma result in the excessive proliferation of keratinocytes and secretion of inflammatory cytokines. Altered metabolism is associated with the activation of MTORC signaling pathway and transcription factors such as HIF and S6K1. Therefore, MTORC1 can be a target for the treatment of psoriasis. Additionally, there are diabetes drugs and lipid-lowering drugs including TZDs, GLP-1 RAs, Metformin, statins and fibrates, which improve both metabolic levels and psoriasis symptoms.In psoriasis, enhanced glycolysis, glutamine metabolism and altered fatty acid composition in the psoriatic lesion and plasma result in the excessive proliferation of keratinocytes and secretion of inflammatory cytokines. Altered metabolism is associated with the activation of MTORC signaling pathway and transcription factors such as HIF and S6K1. Therefore, MTORC1 can be a target for the treatment of psoriasis. Additionally, there are diabetes drugs and lipid-lowering drugs including TZDs, GLP-1 RAs, Metformin, statins and fibrates, which improve both metabolic levels and psoriasis symptoms.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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