COVID-19 is a viral respiratory disease caused by the severe acute respiratory syndrome-Coronavirus type 2 (SARS-CoV-2). Patients with this disease may be more prone to venous or arterial thrombosis ...because of the activation of many factors involved in it, including inflammation, platelet activation and endothelial dysfunction. Interferon gamma inducible protein-10 (IP-10), monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein 1-alpha (MIP1α) are cytokines related to thrombosis. Therefore, this study focused on these three indicators in COVID-19, with the hope to find biomarkers that are associated with patients' outcome.
This is a retrospective single-center study involving 74 severe and critically ill COVID-19 patients recruited from the ICU department of the Tongji Hospital in Wuhan, China. The patients were divided into two groups: severe patients and critically ill patients. The serum IP-10, MCP-1 and MIP1α level in both groups was detected using the enzyme-linked immunosorbent assay (ELISA) kit. The clinical symptoms, laboratory test results, and the outcome of COVID-19 patients were retrospectively analyzed.
The serum IP-10 and MCP-1 level in critically ill patients was significantly higher than that in severe patients (P < 0.001). However, no statistical difference in MIP1α between the two groups was found. The analysis of dynamic changes showed that these indicators remarkably increased in patients with poor prognosis. Since the selected patients were severe or critically ill, no significant difference was observed between survival and death.
IP-10 and MCP-1 are biomarkers associated with the severity of COVID-19 disease and can be related to the risk of death in COVID-19 patients.
The outer membrane (OM) of Gram-negative bacteria serves as a selective permeability barrier that allows entry of essential nutrients while excluding toxic compounds, including antibiotics. The OM is ...asymmetric and contains an outer leaflet of lipopolysaccharides (LPS) or lipooligosaccharides (LOS) and an inner leaflet of glycerophospholipids (GPL). We screened
transposon mutants and identified a number of mutants with OM defects, including an ABC transporter system homologous to the Mla system in
We further show that this opportunistic, antibiotic-resistant pathogen uses this multicomponent protein complex and ATP hydrolysis at the inner membrane to promote GPL export to the OM. The broad conservation of the Mla system in Gram-negative bacteria suggests the system may play a conserved role in OM biogenesis. The importance of the Mla system to
OM integrity and antibiotic sensitivity suggests that its components may serve as new antimicrobial therapeutic targets.
Voltage-gated sodium (Na
) channels initiate action potentials. Fast inactivation of Na
channels, mediated by an Ile-Phe-Met motif, is crucial for preventing hyperexcitability and regulating firing ...frequency. Here we present cryo-electron microscopy structure of Na
Eh from the coccolithophore Emiliania huxleyi, which reveals an unexpected molecular gating mechanism for Na
channel fast inactivation independent of the Ile-Phe-Met motif. An N-terminal helix of Na
Eh plugs into the open activation gate and blocks it. The binding pose of the helix is stabilized by multiple electrostatic interactions. Deletion of the helix or mutations blocking the electrostatic interactions completely abolished the fast inactivation. These strong interactions enable rapid inactivation, but also delay recovery from fast inactivation, which is ~160-fold slower than human Na
channels. Together, our results provide mechanistic insights into fast inactivation of Na
Eh that fundamentally differs from the conventional local allosteric inhibition, revealing both surprising structural diversity and functional conservation of ion channel inactivation.
Multidrug resistance is a serious threat to public health. Proton motive force-driven antiporters from the major facilitator superfamily (MFS) constitute a major group of multidrug-resistance ...transporters. Currently, no reports on crystal structures of MFS antiporters in complex with their substrates exist. The E. coli MdfA transporter is a well-studied model system for biochemical analyses of multidrug-resistance MFS antiporters. Here, we report three crystal structures of MdfA-ligand complexes at resolutions up to 2.0 Å, all in the inward-facing conformation. The substrate-binding site sits proximal to the conserved acidic residue, D34. Our mutagenesis studies support the structural observations of the substrate-binding mode and the notion that D34 responds to substrate binding by adjusting its protonation status. Taken together, our data unveil the substrate-binding mode of MFS antiporters and suggest a mechanism of transport via this group of transporters.
Biosynthetic enzymes evolutionarily gain novel functions, thereby expanding the structural diversity of natural products to the benefit of host organisms. Diels-Alderases (DAs), functionally unique ...enzymes catalysing 4 + 2 cycloaddition reactions, have received considerable research interest. However, their evolutionary mechanisms remain obscure. Here, we investigate the evolutionary origins of the intermolecular DAs in the biosynthesis of Moraceae plant-derived Diels-Alder-type secondary metabolites. Our findings suggest that these DAs have evolved from an ancestor functioning as a flavin adenine dinucleotide (FAD)-dependent oxidocyclase (OC), which catalyses the oxidative cyclisation reactions of isoprenoid-substituted phenolic compounds. Through crystal structure determination, computational calculations, and site-directed mutagenesis experiments, we identified several critical substitutions, including S348L, A357L, D389E and H418R that alter the substrate-binding mode and enable the OCs to gain intermolecular DA activity during evolution. This work provides mechanistic insights into the evolutionary rationale of DAs and paves the way for mining and engineering new DAs from other protein families.
The major facilitator superfamily (MFS) is the largest family of secondary active transporters and is present in all life kingdoms. Detailed structural basis of the substrate transport and ...energycoupling mechanisms of these proteins remain to be elucidated. YajR is a putative proton-driven MFS transporter found in many Gram-negative bacteria. Here we report the crystal structure of Escherichia coli YajR at 3.15 Å resolution in an outward-facing conformation. In addition to having the 12 canonical transmembrane helices, the YajR structure includes a unique 65-residue C-terminal domain which is independently stable. The structure is unique in illustrating the functional role of "sequence motif A." This highly conserved element is seen to stabilize the outward conformation of YajR and suggests a general mechanism for the conformational change between the inward and outward states of the MFS transporters.
Membrane-integrated type II phosphatidic acid phosphatases (PAP2s) are important for numerous bacterial to human biological processes, including glucose transport, lipid metabolism, and signaling. ...Escherichia coli phosphatidylglycerol-phosphate phosphatase B (ecPgpB) catalyzes removing the terminal phosphate group from a lipid carrier, undecaprenyl pyrophosphate, and is essential for transport of many hydrophilic small molecules across the membrane. We determined the crystal structure of ecPgpB at a resolution of 3.2 Å. This structure shares a similar folding topology and a nearly identical active site with soluble PAP2 enzymes. However, the substrate binding mechanism appears to be fundamentally different from that in soluble PAP2 enzymes. In ecPgpB, the potential substrate entrance to the active site is located in a cleft formed by a V-shaped transmembrane helix pair, allowing lateral movement of the lipid substrate entering the active site from the membrane lipid bilayer. Activity assays of point mutations confirmed the importance of the catalytic residues and potential residues involved in phosphate binding. The structure also suggests an induced-fit mechanism for the substrate binding. The 3D structure of ecPgpB serves as a prototype to study eukaryotic PAP2 enzymes, including human glucose-6-phosphatase, a key enzyme in the homeostatic regulation of blood glucose concentrations.
The
subsp.
serovar Typhimurium PhoPQ two-component system is activated within the intracellular phagosome environment, where it promotes remodeling of the outer membrane and resistance to innate ...immune antimicrobial peptides. Maintenance of the PhoPQ-regulated outer membrane barrier requires PbgA, an inner membrane protein with a transmembrane domain essential for growth, and a periplasmic domain required for PhoPQ-activated increases in outer membrane cardiolipin. Here, we report the crystal structure of cardiolipin-bound PbgA, adopting a novel transmembrane fold that features a cardiolipin binding site in close proximity to a long and deep cleft spanning the lipid bilayer. The end of the cleft extends into the periplasmic domain of the protein, which is structurally coupled to the transmembrane domain via a functionally critical C-terminal helix. In conjunction with a conserved putative catalytic dyad situated at the middle of the cleft, our structural and mutational analyses suggest that PbgA is a multifunction membrane protein that mediates cardiolipin transport, a function essential for growth, and perhaps catalysis of an unknown enzymatic reaction.
Gram-negative bacteria cause many types of infections and have become increasingly resistant to available antibiotic drugs. The outer membrane serves as an important barrier that protects bacteria against antibiotics and other toxic compounds. This outer membrane barrier function is regulated when bacteria are in host environments, and the protein PbgA contributes significantly to this increased barrier function by transporting cardiolipin to the outer membrane. We determined the crystal structure of PbgA in complex with cardiolipin and propose a model for its function. Knowledge of the mechanisms of outer membrane assembly and integrity can greatly contribute to the development of new and effective antibiotics, and this structural information may be useful in this regard.
The sodium-activated Slo2.2 channel is abundantly expressed in the brain, playing a critical role in regulating neuronal excitability. The Na+-binding site and the underlying mechanisms of ...Na+-dependent activation remain unclear. Here, we present cryoelectron microscopy (cryo-EM) structures of human Slo2.2 in closed, open, and inhibitor-bound form at resolutions of 2.6–3.2 Å, revealing gating mechanisms of Slo2.2 regulation by cations and a potent inhibitor. The cytoplasmic gating ring domain of the closed Slo2.2 harbors multiple K+ and Zn2+ sites, which stabilize the channel in the closed conformation. The open Slo2.2 structure reveals at least two Na+-sensitive sites where Na+ binding induces expansion and rotation of the gating ring that opens the inner gate. Furthermore, a potent inhibitor wedges into a pocket formed by pore helix and S6 helix and blocks the pore. Together, our results provide a comprehensive structural framework for the investigation of Slo2.2 channel gating, Na+ sensation, and inhibition.
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•The high-resolution EM structures of hSlo2.2 are shown in the presence and absence of Na+•Multiple cation-binding sites in Slo2.2 and their modulation of Slo2.2 gating are revealed•Possible lipids bind to the inner gate of Slo2.2, which may be involved in channel gating•Inhibitor C23 wedges into a pocket formed by pore helix and S6 helix and blocks the pore
Zhang et al. describe the cryo-EM structures of human Slo2.2 in the closed, open, and inhibitor-bound form at resolutions of 2.6–3.2 Å and propose the molecular mechanisms of Slo2.2 regulation by cations and potent inhibitor Compound 23, which contribute to the understanding of Slo2.2 gating.
With the widespread use of immune checkpoint inhibitors to treat various cancers, pulmonary toxicity has become a topic of increasing concern. Anti-melanoma differentiation-associated gene 5 ...(anti-MDA5) antibodies are strongly associated with rapidly progressive interstitial lung disease (RP-ILD) in patients with clinically amyopathic dermatomyositis. However, anti-MDA5 antibody expression has not been reported in patients with immune-related adverse events. We present the case of a 74-year-old man with lung adenocarcinoma who developed RP-ILD after treatment with immune checkpoint inhibitors. Further investigation revealed multiple autoantibodies, including anti-MDA5 antibodies. He initially responded to systemic glucocorticoids, immunosuppressants, and tocilizumab but eventually died from worsening pneumomediastinum. This case is the first one to suggest that checkpoint inhibitor pneumonitis can present as RP-ILD with positive anti-MDA5 antibodies, which may be predictive of a poor prognosis.
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