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Significance ATP8B1 is a P4 ATPase that maintains membrane asymmetry by transporting phospholipids across the cell membrane. Disturbance of lipid asymmetry will lead to the imbalance of the cell membrane and eventually, cell death. Thus, defects in ATP8B1 are usually associated with severe human diseases, such as intrahepatic cholestasis. The present structures of ATP8B1 complexed with its auxiliary noncatalytic partners CDC50A and CDC50B reveal an autoinhibited state of ATP8B1 that could be released upon substrate binding. Moreover, release of this autoinhibition could be facilitated by the bile acids, which are key factors that alter the membrane asymmetry of hepatocytes. This enabled us to figure out a feedback loop of bile acids and lipids across the cell membrane.

The human P4-type ATPase ATP8B1 in complex with the auxiliary noncatalytic protein CDC50A or CDC50B mediates the transport of cell membrane lipids from the outer to the inner membrane leaflet, which is crucial to maintain the asymmetry of membrane lipid. Its dysfunction usually leads to imbalance of bile acid circulation, and eventually causing intrahepatic cholestasis diseases. Here we found that both ATP8B1-CDC50A and ATP8B1-CDC50B possess a higher ATPase activity in the presence of the most favored substrate phosphatidylserine (PS); and moreover, the PS-stimulated activity could be augmented upon the addition of bile acids. The cryo-electron microscopy structures of ATP8B1-CDC50A at 3.36 Å and ATP8B1-CDC50B at 3.39 Å enabled us to capture an unprecedented phosphorylated and autoinhibited state, with the N- and C-terminal tails separately inserting into the cytoplasmic inter-domain clefts of ATP8B1. The PS-bound ATP8B1-CDC50A structure at 3.98 Å indicated the autoinhibited state could be released upon PS binding. Structural analysis combined with mutagenesis revealed the residues that determine the substrate specificity, and a unique positively charged loop in the phosphorylated domain of ATP8B1 for the recruitment of bile acids. Altogether, we updated the Post-Albers transport cycle, with an extra autoinhibited state of ATP8B1, which could be activated upon substrate binding. These findings not only provide structural insights into the ATP8B1-mediated restoration of human membrane lipid asymmetry during bile acid circulation, but also advance our understanding on the molecular mechanism of P-type ATPases.

SUMMARYBrain regeneration requires a precise coordination of complex responses in a time- and region-specific manner. Identifying key cell types and molecules that direct brain regeneration would provide potential targets for the advance of regenerative medicine. However, progress in the field has been hampered largely due to limited regeneration capacity of the mammalian brain and understanding of the regeneration process at both cellular and molecular level. Here, using axolotl brain with extrodinary regeneration ability upon injury, and the SpaTial Enhanced REsolution Omics-sequencing (Stereo-seq), we reconstructed the first architecture of axolotl telencephalon with gene expression profiling at single-cell resolution, and fine cell dynamics maps throughout development and regeneration. Intriguingly, we discovered a marked heterogeneity of radial glial cell (RGC) types with distinct behaviors. Of note, one subtype of RGCs is activated since early regeneration stages and proliferates while other RGCs remain dormant. Such RGC subtype appears to be the major cell population involved in early wound healing response and gradually covers the injured area before presumably transformed into the lost neurons. Altogether, our work systematically decoded the complex cellular and molecular dynamics of axolotl telencephalon in development and regeneration, laying the foundation for studying the regulatory mechanism of brain regeneration in the future.

As one of the most abundant bacteria in the human oral cavity, Fusobacterium nucleatum is closely involved in various oral diseases and is also a risk factor for other diseases. The peptidases of F. nucleatum can digest exogenous peptides into amino acids to satisfy its nutrient requirements. Here, a putative F. nucleatum peptidase, termed S9Cfn, which belongs to the S9C peptidase family was identified. Enzymatic activity assays combined with mass-spectrometric analysis revealed that S9Cfn is a carboxypeptidase, but not an aminopeptidase as previously annotated. The crystal structure of the S9Cfn tetramer was solved at 2.6 Å resolution and was found to contain a pair of oligomeric pores in the center. Structural analysis, together with site-directed mutagenesis and enzymatic activity assays, revealed a substrate-entrance tunnel that extends from each oligomeric pore to the catalytic triad, adjacent to which three conserved arginine residues are responsible for substrate binding. Moreover, comparison with other S9 peptidase structures indicated drastic conformational changes of the oligomeric pores during the catalytic cycle. Together, these findings increase the knowledge of this unique type of tetrameric carboxypeptidase and provide insight into the homeostatic control of microbiota in the human oral cavity.

The spr0693-spr0694-spr0695 operon of Streptococcus pneumoniae encodes a putative ATP-binding cassette (ABC)-type efflux pump involved in the resistance of antibiotics and antimicrobial peptides. Here we report the crystal structures of Spr0694–0695 at 3.3 Å and Spr0693 at 3.0 Å resolution, revealing a MacAB-like efflux pump. The dimeric Spr0694–0695 adopts a non-canonical fold of ABC transporter, the transmembrane domain of which consists of eight tightly packed transmembrane helices with an insertion of extracellular domain between the first and second helices, whereas Spr0693 forms a nanotube channel docked onto the ABC transporter. Structural analyses combined with ATPase activity and antimicrobial susceptibility assays, enable us to propose a putative substrate-entrance tunnel with a lateral access controlled by a guard helix. Altogether, our findings provide structural insights and putative transport mechanism of a MacAB-like efflux pump in Gram-positive bacteria., Bacterial ATP-binding cassette (ABC)-type efflux pumps are involved in the resistance of antibiotics and antimicrobial peptides. Here authors report the crystal structures and ATPase activity of the MacAB-like efflux pump from Streptococcus pneumonia and describe a putative substrate transport mechanism.

Different from the common understanding that crystallization deteriorates the degradation capability of amorphous alloys, we show here that the Fe-based multi-phase nanocrystalline ribbons (Fe-MNRs) exhibit 3 and 17 times higher degradation rate than its amorphous counterpart and the conventional zero valent iron powders, respectively. The formation of multi-phase nanocrystals and nanoporous structure resulted from selective corrosion during degradation is responsible for the high degradation capability of Fe-MNRs. The present results suggest that suitable nano-crystallization annealing treatment could be a novel approach to enhance the degradation capability of Fe-based amorphous alloys.

Fe-based metallic glasses (MGs) are among the most interesting in the area of MG materials, due to their superior properties such as high degradation capability of azo dyes. However, the ways that factors influence the degradation capability of MGs towards azo dyes are still unclear. From this reason, the effect of residual stress on degradation capability of Fe-based MG was investigated. (Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 ) 91.5 Ni 8.5 as-cast MG ribbons and annealed MG ribbons were prepared and subjected to degrade Orange II solutions. The as-cast ribbons completely degrade the azo dye within 60 min, the ribbons annealed at 673 K take 120 min, although the annealed ribbons still sustain metastable glassy state. Surface morphology and magnetic domain pattern of the ribbons were characterized carefully. The results demonstrate that the inhomogeneous residual stress could contribute to high degradation capability of the as-cast MG ribbons by generating stress gradient cell and increasing active sites. Therefore, increasing residual stress can be a novel clue to enhance degradation capability of materials.

Background Electromagnetic hypersensitivity refers to health effects attributed to electromagnetic fields (EMF) exposure and has been formally named “idiopathic environmental intolerance attributed to electromagnetic fields” (IEI-EMF) by the World Health Organization. Because of the growing use of cell phones, IEI-EMF has become a global public health concern. A survey in 2007 in Taiwan showed that the prevalence rate of IEI-EMF was 13.3%, which is higher than rates in studies conducted previously. The survey also found that the rate was higher in women. Methods To evaluate whether the prevalence rate of IEI-EMF is increasing and to verify the higher risk in women, we conducted a nationwide questionnaire survey using the same methods as the 2007 survey to assess the change in the prevalence rate of IEI-EMF in Taiwan. We also conducted a review of the literature and a meta-analysis to evaluate the changes in the prevalence rate around the world. Results On the basis of the representative sample of 3303 participants, we found that the prevalence rate of IEI-EMF in Taiwan declined from 13.3% to 4.6% over a period of 5 years. The literature review also found the prevalence rates in other countries to be decreasing, instead of increasing as predicted previously. The meta-analysis of the data from the literature showed that women are more likely to have IEI-EMF than men, with an odds ratio of 1.19 (95% confidence interval: 1.01—1.40). Conclusions We found the prevalence rate of IEI-EMF has been declining, instead of increasing as predicted previously. Women are more likely to report having IEI-EMF than men. Further studies to explore the causes leading to the declines may help the public, scientific community, and government deal with idiopathic intolerance to other environmental exposures.

For simulating the wind load strength effect so as to detect the opening and closing performance of the aerodynamic braking device and the reliability of its opening and closing mechanism with the wind load caused by high speed flow field, the wind load test-bed is to build. Wind channel, as the equipment to turn a high pressure flow into a relatively high speed advection, is one of its important components. This paper focuses on the design of the shape of the wind channel. By the means of flow field simulation analysis, with the indexes of the wind load size, the pressure distribution and the flow equality, the shape optimization of the wind channel is realized.

Based on the original Electronically Controlled Pneumatic (ECP) brake system of the heavy-haul freight train and SIMULINK, in this paper we establishes the vehicle longitudinal dynamics model and a new braking control mode (deceleration control) in order to reduce the shock caused by the impulse of the vehicles to the coupler so as to lessen the danger of coupler fracture. The author adopts the Smith-PID control compensating method as the core of the deceleration control so as to control the vehicle longitudinal dynamics model. Furthermore, by calculating the variation of the coupler force and comparing with the results of the original braking force control method, theoretically we can draw conclusion that deceleration control has high feasibility and superiority.