In eukaryotes, most secretory and membrane proteins are targeted by an N‐terminal signal sequence to the endoplasmic reticulum, where the trimeric Sec61 complex serves as protein‐conducting channel ...(PCC). In the post‐translational mode, fully synthesized proteins are recognized by a specialized channel additionally containing the Sec62, Sec63, Sec71, and Sec72 subunits. Recent structures of this Sec complex in the idle state revealed the overall architecture in a pre‐opened state. Here, we present a cryo‐EM structure of the yeast Sec complex bound to a substrate, and a crystal structure of the Sec62 cytosolic domain. The signal sequence is inserted into the lateral gate of Sec61α similar to previous structures, yet, with the gate adopting an even more open conformation. The signal sequence is flanked by two Sec62 transmembrane helices, the cytoplasmic N‐terminal domain of Sec62 is more rigidly positioned, and the plug domain is relocated. We crystallized the Sec62 domain and mapped its interaction with the C‐terminus of Sec63. Together, we obtained a near‐complete and integrated model of the active Sec complex.
SYNOPSIS
The overall architecture of the eukaryotic SecY/Sec61 channel for post‐translational protein translocation, and how it recognizes N‐terminal signal sequences in transported proteins, remain unclear. Here, structural analyses reveal the molecular architecture of the engaged yeast Sec complex, which binds the signal sequence in a unique open conformation.
Cryo‐EM structures of the heptameric Sec complex reveal the conformational transition from the partially open apo‐state to the fully open signal sequence‐bound state.
The signal sequence binds the lateral gate of the Sec61 complex, which is stabilized by the transmembrane helices of the Sec62 subunit.
The X‐ray structure of the N‐terminal cytoplasmic domain of Sec62 reveals a novel fold that is coordinated by the phosphorylated C‐terminal peptide of the Sec63 subunit.
Cryo‐electron microscopy and X‐ray crystallography studies reveal the molecular architecture of the engaged eukaryotic heptameric Sec complex, binding the protein signal sequence in an open conformation.
Heterogeneous nuclear ribonucleoprotein K (hnRNPK) is an RNA/DNA-binding protein involved in chromatin remodeling, RNA processing and the DNA damage response. In addition, increased hnRNPK expression ...has been associated with tumor development and progression. A variety of post-translational modifications of hnRNPK have been identified and shown to regulate hnRNPK function, including phosphorylation, ubiquitination, sumoylation and methylation. However, the functional significance of hnRNPK arginine methylation remains unclear. In the present study, we demonstrated that the methylation of two essential arginines, Arg296 and Arg299, on hnRNPK inhibited a nearby Ser302 phosphorylation that was mediated through the pro-apoptotic kinase PKCδ. Notably, the engineered U2OS cells carrying an Arg296/Arg299 methylation-defective hnRNPK mutant exhibited increased apoptosis upon DNA damage. While such elevated apoptosis can be diminished through addition with wild-type hnRNPK, we further demonstrated that this increased apoptosis occurred through both intrinsic and extrinsic pathways and was p53 independent, at least in part. Here, we provide the first evidence that the arginine methylation of hnRNPK negatively regulates cell apoptosis through PKCδ-mediated signaling during DNA damage, which is essential for the anti-apoptotic role of hnRNPK in apoptosis and the evasion of apoptosis in cancer cells.
PmrA, an OmpR/PhoB family response regulator, manages genes for antibiotic resistance. Phosphorylation of OmpR/PhoB response regulator induces the formation of a symmetric dimer in the N-terminal ...receiver domain (REC), promoting two C-terminal DNA-binding domains (DBDs) to recognize promoter DNA to elicit adaptive responses. Recently, determination of the KdpE-DNA complex structure revealed an REC-DBD interface in the upstream protomer that may be necessary for transcription activation. Here, we report the 3.2-Å-resolution crystal structure of the PmrA-DNA complex, which reveals a similar yet different REC-DBD interface. However, NMR studies show that in the DNA-bound state, two domains tumble separately and an REC-DBD interaction is transiently populated in solution. Reporter gene analyses of PmrA variants with altered interface residues suggest that the interface is not crucial for supporting gene expression. We propose that REC-DBD interdomain dynamics and the DBD-DBD interface help PmrA interact with RNA polymerase holoenzyme to activate downstream gene transcription.
碩士
國立陽明大學
生命科學系暨基因體科學研究所
102
The PmrA/PmrB two-component system regulates polymyxin-resistance in Gram-negative bacteria. After phosphorylated by the histidine kinase PmrB, the N-terminal receiver ...domain (RD) of the response regulator PmrA then forms a dimer and the C-terminal DNA-binding domain (DBD) recognizes the tandem repeat sequences of target promoters, initiating transcription of polymyxin-resistant genes.
We solved the 3.2-Å resolution crystal structure of the BeF3−-activated full-length Klebsiella pneumoniae PmrA in complex with a 25-bp DNA. The dimerization of RD and the DBD-DNA interaction is consistent with previous study. However, the intramolecular RD-DBD interface of the two protomers is asymmetric: in one protomer the RD contacts the DBD with a buried surface area of 627.5 Å2, whereas in the other one the two domains are only connected by a linker. This asymmetric interaction may play a role in the PmrA-DNA binding and stabilize the transactivation loop in DBD, which interacts with the σ70 subunit and activates transcription.
In the chemical reaction that proceeds in a high-temperature proton exchange membrane fuel cell stack (HT-PEMFC stack), the internal local temperature, voltage, pressure, flow and current ...nonuniformity may cause poor membrane material durability and nonuniform fuel distribution, thus influencing the performance and lifetime of the fuel cell stack. In this paper micro-electro-mechanical systems (MEMS) are utilized to develop a high-temperature electrochemical environment-resistant five-in-one micro-sensor embedded in the cathode channel plate of an HT-PEMFC stack, and materials and process parameters are appropriately selected to protect the micro-sensor against failure or destruction during long-term operation. In-situ measurement of the local temperature, voltage, pressure, flow and current distributions in the HT-PEMFC stack is carried out. This integrated micro-sensor has five functions, and is favorably characterized by small size, good acid resistance and temperature resistance, quick response, real-time measurement, and the goal is being able to be put in any place for measurement without affecting the performance of the battery.
Data curation for a hospital-based cancer registry heavily relies on the labor-intensive manual abstraction process by cancer registrars to identify cancer-related information from free-text ...electronic health records. To streamline this process, a natural language processing system incorporating a hybrid of deep learning-based and rule-based approaches for identifying lung cancer registry-related concepts, along with a symbolic expert system that generates registry coding based on weighted rules, was developed. The system is integrated with the hospital information system at a medical center to provide cancer registrars with a patient journey visualization platform. The embedded system offers a comprehensive view of patient reports annotated with significant registry concepts to facilitate the manual coding process and elevate overall quality. Extensive evaluations, including comparisons with state-of-the-art methods, were conducted using a lung cancer dataset comprising 1428 patients from the medical center. The experimental results illustrate the effectiveness of the developed system, consistently achieving F1-scores of 0.85 and 1.00 across 30 coding items. Registrar feedback highlights the system’s reliability as a tool for assisting and auditing the abstraction. By presenting key registry items along the timeline of a patient’s reports with accurate code predictions, the system improves the quality of registrar outcomes and reduces the labor resources and time required for data abstraction. Our study highlights advancements in cancer registry coding practices, demonstrating that the proposed hybrid weighted neural-symbolic cancer registry system is reliable and efficient for assisting cancer registrars in the coding workflow and contributing to clinical outcomes.
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•Home-made three-in-one flexible micro sensor can be placed anywhere in a high temperature proton exchange membrane fuel cell stack.•Three-in-one flexible micro sensors are three functions, ...compactness, acid corrosion resistance, good temperature tolerance, quick response, real-time measurement and optional location.•In-situ diagnosis local temperature, voltage and flow information of a high temperature proton exchange membrane fuel cell stack.
The chemical reaction process of high temperature proton exchange membrane fuel cell stack (HT-PEMFC stack) results in poor membrane material durability and nonuniform fuel distribution and influences the fuel cell stack performance and life. The local temperature, voltage and flow inside the high temperature fuel cell stack are three major factors, so this study aims at the three physical phenomena.
This study used micro-electro-mechanical systems (MEMS) technology to develop a high temperature electrochemical environment resistant integrated (temperature, voltage and flow) microsensor on a 40μm thick stainless steel substrate, the protective layer was made of polyimide (PI) with better temperature tolerance. This study also captured the internal information of local temperature and voltage and flow inside the high temperature fuel cell stack instantly. The 100-h persistent effect test at operating temperature of 160°C and current 6.28A validated the reliability of the high temperature electrochemical environment resistant integrated microsensor. The experimental results showed the nonuniform temperature and flow distributions in the high temperature fuel cell stack resulted in high temperature contrast and nonuniform voltage distribution, and there was hot stack.
To evaluate the prognostic potential of expression of hormone receptors in malignant mammary gland tumors of dogs. Design-Cohort study.
89 female dogs with malignant mammary gland tumors and 24 ...female dogs with benign mammary gland tumors.
Female dogs with malignant (n = 89 dogs) and benign (24) mammary gland tumors were evaluated to determine the prognostic value of the expression of estrogen receptor (ER)A or the progesterone receptor (PR), as determined by use of immunohistochemical methods.
In this study, 68 (60.2%) and 88 (77.9%) of the 113 dogs with mammary gland tumors had expression of ERA and PR, respectively. Expression of ERA and PR was detected proportionately more frequently in benign tumors (23/24 95.8% and 24/24 100%, respectively) than in malignant tumors (45/89 50.6% and 64/89 71.9%). Percentage of tumors with positive results for ERA and PR was significantly higher in tumors < 5 cm in diameter; as clinical stage I, II, or III; and without metastasis to lymph nodes or distant metastasis. However, only PR expression in tumor cells was significantly associated with 1-year survival after surgical removal of the tumor. Moreover, dogs with malignant tumors expressing ERA and PR had a significantly higher survival rate, compared with the rate for dogs with malignant tumors expressing ERA but not PR.
These findings strongly suggested that expression of PR could be used as a prognostic factor for survival, especially in female dogs with malignant mammary gland tumors with ERA expression.
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