SUMMARY Thermosomes are group II chaperonins responsible for protein refolding in an ATP-dependent manner. Little is known regarding the conformational changes of thermosomes during their functional cycle due to lack of high-resolution structure in open state. Here we report the first complete crystal structure of thermosome (rATcpnβ) in open state from Acidianus tengchongensis. There is a ~30° rotation of the apical and lid domains compared to the previous closed structure. Besides, the structure reveals a conspicuous hydrophobic patch in the lid domain and residues locating in this patch are conserved across species. Both the closed and open forms of rATcpnβ were also reconstructed by electron microscopy (EM). Structural fitting revealed the detailed conformational change from open to closed state. Structural comparison as well as protease K digestion indicated only ATP binding without hydrolysis does not induce chamber closure of thermosome.

Whooping cough (pertussis) is a highly contagious acute respiratory illness of humans caused by the Gram-negative bacterial pathogen Bordetella pertussis. The AT (autotransporter) BrkA (Bordetella serum-resistance killing protein A) is an important B. pertussis virulence factor that confers serum resistance and mediates adherence. In the present study, we have solved the crystal structure of the BrkA β-domain at 3 Å (1 Å=0.1 nm) resolution. Special features are a hairpin-like structure formed by the external loop L4, which is observed fortuitously sitting inside the pore of the crystallographic adjacent β-domain, and a previously undiscovered hydrophobic cavity formed by patches on loop L4 and β-strands S5 and S6. This adopts a ubiquitous structure characteristic of all AT β-domains. Mutagenesis studies have demonstrated that the hairpin-like structure and hydrophobic cavity are crucial for BrkA passenger domain (virulence effector) translocation. This structure helps in understanding the molecular mechanism of AT assembly and secretion and provides a potential target for anti-pertussis drug design.

Bacterial vaginosis (BV) is the most common vaginal infection found inwomen in the world. Due to increasing drug-resistance of virulent pathogen such as Gardnerella vaginalis (G. vaginalis), more than half of BV patients suffer recurrence after antibotics treatment. Here, metastable iron sulfides (mFeS) act in a Gram-dependent manner to kill bacteria, with the ability to counteract resistant G. vaginalis for BV treatment. With screening of iron sulfide minerals, metastable Fe 3 S 4 shows suppressive effect on bacterial growth with an order: Gram-variable G. vaginalis >Gram-negative bacteria>> Gram-positive bacteria. Further studies on mechanism of action (MoA) discover that the polysulfide species released from Fe 3 S 4 selectively permeate bacteria with thin wall and subsequently interrupt energy metabolism by inhibiting glucokinase in glycolysis, and is further synergized by simultaneously released ferrous iron that induces bactericidal damage. Such multiple MoAs enable Fe 3 S 4 to counteract G. vaginalis strains with metronidazole-resistance and persisters in biofilm or intracellular vacuole, without developing new drug resistance and killing probiotic bacteria. The Fe 3 S 4 regimens successfully ameliorate BV with resistant G. vaginalis in mouse models and eliminate pathogens from patients suffering BV. Collectively, mFeS represent an antibacterial alternative with distinct MoA able to treat challenged BV and improve women health.

No abstract

Phosphatidic acid (PA), the simplest phospholipid, acts as a key metabolic intermediate and second messenger that impacts diverse cellular and physiological processes across species ranging from microbes to plants and mammals. The cellular levels of PA dynamically change in response to stimuli, and multiple enzymatic reactions can mediate its production and degradation. PA acts as a signalling molecule and regulates various cellular processes via its effects on membrane tethering, enzymatic activities of target proteins, and vesicular trafficking. Because of its unique physicochemical properties compared to other phospholipids, PA has emerged as a class of new lipid mediators influencing membrane structure, dynamics, and protein interactions. This review summarizes the biosynthesis, dynamics, and cellular functions and properties of PA.

Background and objective Overuse of β2‐adrenoceptor agonist bronchodilators causes receptor desensitization, resulting in decreased efficacy and an increased risk of death in asthma patients. This is a critical unmet problem in asthma management, and novel drugs are urgently needed. Here, we report that osthole, a coumarin derived from a traditional Chinese medicine, induces complete relaxation of preconstricted airways in mouse precision‐cut lung slices, irrespective of β2‐adrenoceptor desensitization. Methods Mouse precision‐cut lung slices as an in vitro model were used to analyze airway relaxation. The cAMP level in human airway smooth muscle (ASM) or HEK293 cells was determined by phosphorylation of vasodilator‐stimulated phosphoprotein using Western blot or cAMP dependent reporter luciferase assay. The secretion of prostaglandin E2 (PGE2) in ASM cells or lung slices was measured by ELISA assay. The effect of osthole on airway hyperresponsiveness (AHR) was measured in both house dust mite (HDM)‐sensitized mice and naïve regulator of G‐protein signaling 2 (RGS2) KO mice. The binding sites of osthole with PDE4D5 catalytic domain were analyzed by crystallization and X‐ray diffraction. Results Osthole administered in vivo ameliorates AHR, a hallmark of asthma, in murine asthma models. Mechanistic studies revealed that osthole inhibits phosphodiesterase 4D (PDE4D) activity to amplify endogenous PGE2 signaling in ASM cells, which eventually triggers cAMP/protein kinase A‐dependent relaxation of airways. The crystal structure of the PDE4D complexed with osthole reveals that osthole binds to the catalytic site to prevent cAMP binding and hydrolysis. Together, our studies elucidate a specific molecular target and mechanism by which osthole induces airway relaxation. Conclusion Identification of osthole binding sites on PDE4D will guide further development of novel therapeutics for β2‐adrenoceptor agonist‐resistant asthma. Support or Funding Information This work was supported in part by the National Institutes of Health (R01HL116849) and Nebraska State LB595 Research Program, USA; the National Laboratory of Biomacromolecules and the Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences (CAS); the CAS/SAFEA International Partnership Program for Creative Research Teams; the National Key R&D Program of China (2017YFA0205501); the National Natural Science Foundation of China (21777192 and 31500623)

No abstract