Many Gram-negative bacterial pathogens utilize the type III secretion system (T3SS) to inject virulence factors, named effectors, into host cells. These T3SS effectors manipulate host cellular signaling pathways to facilitate bacterial pathogenesis. Death receptor signaling plays an important role in eukaryotic cell death pathways. NleB from enteropathogenic Escherichia coli (EPEC) and SseK1/3 from Salmonella enterica serovar Typhimurium (S. Typhimurium) are T3SS effectors. They are defined as a family of arginine GlcNAc transferase to modify a conserved arginine residue in the death domain (DD) of the death receptor TNFR and their corresponding adaptors to hijack death receptor signaling. Here we identified that these enzymes, NleB, SseK1, and SseK3 could catalyze auto-GlcNAcylation. Residues, including Arg13/53/159/293 in NleB, Arg30/158/339 in SseK1, and Arg153/184/305/335 in SseK3 were identified as the auto-GlcNAcylation sites by mass spectrometry. Mutation of the auto-modification sites of NleB, SseK1, and SseK3 abolished or attenuated the capability of enzyme activity toward their death domain targets during infection. Loss of this ability led to the increased susceptibility of the cells to TNF-or TRAIL-induced cell death during bacterial infection. Overall, our study reveals that the auto-GlcNAcylation of NleB, SseK1, and SseK3 is crucial for their biological activity during infection.
To train inexperienced workers for the construction, production, and maintenance of subsea production systems, a virtual reality simulation platform was developed. The entire framework, software, and hardware platforms of the system were designed and introduced. A multi-person collaborative simulation was achieved based on the high-level architecture protocol. The real-time dynamic calculation software Vortex was used to add physical properties to each geometrical model and set collision detections and motion constraints so that the VR system can reflect the real motion response of the structures in real-time during virtual simulation. Visual simulation software Vega Prime and Vortex were integrated to realise the real-time rendering and drawing of virtual ocean engineering scenes. Thus, a virtual simulation system with large-scale complex scenes based on real-time dynamic calculation and multi-person collaborative operation was established. A typical ocean engineering case of subsea manifold installation was simulated using the virtual simulation system, and the detailed simulation flow was explained. A multibody dynamics system of the ship-cable-subsea manifold was established using Orcaflex to obtain the accurate motion response of the subsea manifold during lowering. In the virtual simulation process, the obtained hydrodynamic calculation results can provide an important guideline and reference to the operators. The developed simulation system is a suitable tool for training ocean engineering workers and realistically simulating ocean operation cases.
In order to achieve high-accuracy self-calibration and traceability of electromagnetic standard voltage transformers, a measurement method that can be used for voltage ratio standard error voltage coefficients is proposed. Using two auxiliary standard voltage transformers, the error variation of the voltage transformer under different voltages can be obtained through three-step measurement. Compared with the traditional error voltage coefficient measurement method and international comparison, the feasibility of the method and the rationality of the uncertainty evaluation of the measurement results are verified. The self-calibration ratio difference measurement uncertainty of the 110 kV standard voltage transformer is better than 5 × 10−6, and the angular difference measurement uncertainty is better than 5 µrad. The method can be used to trace the source of standard devices up to 1000 kV power frequency voltage ratio, which have characteristics such as high accuracy and good stability.
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