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Rational engineering of homospermidine synthase for enhanced catalytic efficiency toward spermidine synthesis

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Synthetic and Systems Biotechnology 2024年第3期9卷 549-557页

作者： Wenjing Liu xiaoxiang hu Yi Yan Yujie Cai The Key Laboratory of Industrial Biotechnology Ministry of EducationSchool of BiotechnologyJiangnan University1800 Lihu RoadWuxiJiangsu214122China

Spermidine is a naturally occurring polyamine widely utilized in the prevention and treatment of various *** spermidine biosynthetic methods have problems such as low efficiency and complex multi-enzyme *** on sequence-structure-function relationships,we engineered the widely studied homospermidine synthase from Blastochloris viridis(BvHSS)and obtained mutants that could catalyze the production of spermidine from 1,3-diaminopropane and *** specific activities of BvHSS and the mutants D361E and E232D+D361E(E232D-D)were 8.72,46.04 and 48.30 U/mg,*** optimal pH for both mutants was 9.0,and the optimal temperature was 50◦*** docking and dynamics simulations revealed that mutating aspartic acid at position 361 to glutamic acid narrowed the substrate binding pocket,promoting stable spermidine ***,mutating glutamic acid at position 232 to aspartic acid enlarged the substrate channel entrance,facilitating substrate entry into the active pocket and enhancing spermidine *** whole-cell catalysis lasting 6 h,D361E and E232D-D synthesized 725.3 and 933.5 mg/L of spermidine,*** study offers a practical approach for single-enzyme catalyzed spermidine synthesis and sheds light on the crucial residues influencing homospermidine synthase catalytic activity in spermidine production.

关键词： Homospermidine synthase Polyamine Site-directed mutagenesis Spermidine Structural analysis

Serum metabolic profile and metabolome genome‑wide association study in chicken

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Journal of Animal Science and Biotechnology 2023年第5期14卷 1926-1940页

作者： Jing Tian Xiaoning Zhu Hanyu Wu Yuzhe Wang xiaoxiang hu State Key Laboratory of Agrobiotechnology College of Biological SciencesChina Agricultural UniversityBeijing 100193China National Research Facility for Phenotypic and Genotypic Analysis of Model Animals(Beijing) China Agricultural UniversityBeijing 100193China

Background Chickens provide globally important livestock *** the genetic and molecular mechanisms underpinning chicken economic traits is crucial for improving their selective *** by a combination of genetic and environmental factors,metabolites are the ultimate expression of physiological processes and can provide key insights into livestock economic ***,the serum metabolite profile and genetic archi-tecture of the metabolome in chickens have not been well *** Here,comprehensive metabolome detection was performed using non-targeted LC–MS/MS on serum from a chicken advanced intercross line(AIL).In total,7,191 metabolites were used to construct a chicken serum metabo-lomics dataset and to comprehensively characterize the serum metabolism of the chicken AIL ***-tory loci affecting metabolites were identified in a metabolome genome-wide association study(mGWAS).There were 10,061 significant SNPs associated with 253 metabolites that were widely distributed across the entire chicken *** functional genes affect metabolite synthesis,metabolism,and *** highlight the key roles of TDH and AASS in amino acids,and ABCB1 and CD36 in *** We constructed a chicken serum metabolite dataset containing 7,191 metabolites to provide a refer-ence for future chicken metabolome characterization ***,we used mGWAS to analyze the genetic basis of chicken metabolic traits and metabolites and to improve chicken breeding.

关键词： Chicken Metabolic traits mGWAS Serum

Expression detection and partial cloning of porcine leptin receptor (OBR) gene

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Chinese Science Bulletin 2001年第5期46卷 396-400页

作者： hu xiaoxiang DAI Rujuan LI Ming WU Changxin College of Animal Science and Technology China Agricultural UniversityBeijing 100094China National Laboratory for Agrobiotechnology China Agricultural UniversityBeijing 100094China

The product of the obesity gene, called leptin, is an important regulator of adiposity, which mainly functions via its regulation of feed intake and energy metabolism. Both obesity gene (ob gene) and leptin receptor gene (OBR gene) are thought to play a major role in controlling of body fat mass as well as body weight. The result of RT-PCR shows that levels of pig OBR mRNA are higher in hypothalamus, lung and liver, and lower expression can be detected in other tissues. Total RNA purified from 11 different organs and tissues have been hybridized with pig OBR cDNA probes. The hybridization signals are shown in 7 organs and tissues. 4.1 and 3.8 kb bands were observed from hypothalamus, whereas 3.8 and 3.5 kb bands were observed in other tissues instead. The nearly complete sequence of the extracellular domain of pig OBR gene was obtained. The homology of sequence is 89.2% between pig and human, 80.3% between pig and mouse. Alignment of the predicted ammo acid sequence of OBR in pig, human and mouse shows

关键词： pig ob (obese) gene OBR (leptin receptor) gene leptin RT-PCR Northern blotting.

A Fuzzy Modified Elastoplastic Friction Model for Parameter Estimation with MHE 36

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A Fuzzy Modified Elastoplastic Friction Model for Parameter ...

The gain of hydrogen peroxide resistance benefits growth fitness in mycobacteria under stress

第36届中国控制会议

作者： Shipeng Fang Changhua hu xiaoxiang hu Hongzeng Li Hi-Tech Institute of Xian

ISBN: (纸本)9781538629185

Friction modeling plays a very important role in control and simulation systems. A lot of dynamic models are proposed to capture most of the friction behavior observed experimentally. Most dynamic models are typically considered to be dependent only on relative speed and relative displacement of contacting surfaces. However, it is known that dynamic characteristics of friction are affected by other factors besides speed and displacement. In this paper, a modified Elastoplastic model is presented in order to closely approximate the Elastoplastic model. In contrast to the Elastoplastic model, the modified model consists of an infinitely differentiable transition function. Such a model is well suited for gradient-based state and parameter estimation methods such as moving horizon estimation. To consider the friction changes caused by many other factors（e.g. load, temperature, lubrication, etc., but without speed and displacement）, a fuzzy system is designed to establish a mapping between the other factors and the modified Elastoplastic model parameters. The complex effects of other factors on friction are fitted through the fuzzy system, while the dynamic characteristics of friction are not lost. Simulation results verify the effectiveness of the proposed model.

关键词： Friction Modified Elastoplastic Model Fuzzy System Moving Horizon Estimation

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Protein & Cell 2014年第3期5卷 182-185页

作者： Xiaojing Li Jun Tao Jiao Han Xinling hu YulingChen Haiteng Deng Guangchun Zhang xiaoxiang hu Kaixia Mi CAS Key Laboratory of Pathogenic Microbiology and Immunology Institute of Microbiology CAS Beijing 100101 China University of Chinese Academy of Sciences Beijing 100082 China School of Life Sciences Tsinghua University Beijing 100084 China School of Life Sciences China Agriculture University Beijing 100094 China Beijing Key Laboratory of Drug Resistance and Resistome Beijing 100101 China

Dear Editor, Tuberculosis （TB） is a formidable challenge to global health and is caused by an ancient pathogen, Mycobacteriurn tuberculosis （WHO, 2010）. In the pre-antibiotic era, TB killed 20% of adults in Europe and North America in the period from the seventeenth to the nineteenth centuries （Wilson, 2005）. Since antibiotics have been included in TB treatment regi- mens, millions of human lives have been saved by this che- motherapy. However, the standard anti-tuberculosis therapy is only effective for drug-susceptible TB but not for multi-drug resistant and extensively drug-resistant TB. Unfortunately, our knowledge of drug resistance in mycobacteria remains unclear and thus hampers the development of new anti- tubercular drugs. The basic mechanisms of drug resistance in mycobacteria are complicated and the outcome of drug resistance stems from evolution in the final analysis. Under- standing the evolutionary strategies used by M. tuberculosis might give new insights into designing control strategies against M. tuberculosis （Little et al,. 2012）.

关键词： hydrogen peroxide resistance benefits formidable challenge global health

Prevention and treatment of gerbil hepatitis E using the programmable CRISPR-Cas13d system

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Genes & Diseases 2024年第4期11卷 94-97页

作者： Chengcheng Zhao Chong Lia Sa Li Hanyu Wu Pengyao Ren Tianlong Liu xiaoxiang hu Ran Zhang State Key Laboratory of Animal Biotech Breeding College of Biological SciencesChina Agricultural UniversityBeijing 100193China Laboratory of Veterinary Pathology and Nanopathology College of Veterinary MedicineChina Agricultural UniversityBeijing 100193China

In recent years,the global incidence of hepatitis E virus(HEV)has been rising,leading to increased morbidity and mortality associated with ***13,a CRISPR effector,shows promise as an antiviral agent against singlestranded RNA ***13d,a type VI-D effector,exhibits higher efficiency in suppressing RNA viruses compared to other type VI ***,its in vivo activity against RNA viruses in mammals remains unknown.

关键词： mortality hepatitis treatment

The LTR of endogenous retrovirus ev21 retains promoter activity and exhibits tissue specific transcription in chicken

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Chinese Science Bulletin 2009年第24期54卷 4664-4670页

作者： LU XiaoQing HAN JinRun LIU XiaoFang LIN Tonghui LI YuLin hu xiaoxiang LI Ning State Key Laboratory of Agrobiotechnology College of Biological Sciences China Agricultural University Beijing 100193 China College of Animal Science & Technology China Agricultural University Beijing 100193 China

Endogenous viruses integrate into the host genome and influence the expression of neighboring genes through their long terminal repeats (LTRs). In this study, we analyzed the promoter, enhancer and transcriptional activities of the chicken endogenous retrovirus ev21 LTR. The LTR was cloned into pGL3-basic and pGL3-promoter luciferase vectors in forward and reverse orientation separately. The luciferase activities were detected respectively in chicken embryonic fibroblast cell, human embryonic kidney cell line, human lung carcinoma cell line, Chinese hamster ovary cell line, and murine melanoma cell line. Relative luciferase activity analysis indicated that the ev21 LTR retained bi-directional promoter activity but no detectable enhancer activity in these cells. The constructs containing the LTR and F1 region show stronger promoter activity than the constructs containing only LTR. The transcriptional pattern of ev21 LTR varied in tissues of late feathering White Leghorn chicken at post-hatch day one. Skin exhibits the highest expression in the tissues examed. Collectively, our results indicate that the ev21 LTR exhibits tissue-type specific expression in White Leghorn chicken, and it also have regulatory potential.

关键词：内源性逆转录病毒启动子活性白来航鸡组织特异性展品铁胚胎成纤维细胞宿主基因组

Effects of fasting and refeeding on expression of MAFbx and MuRF1 in chick skeletal muscle

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Science China(Life Sciences) 2011年第10期54卷 904-907页

作者： LI QingHe LI JinXiu LAN He WANG Nan hu xiaoxiang CHEN Li LI Ning State Key Laboratory for Agrobiotechnology China Agricultural University Beijing 100193 China College of Veterinary Medicine China Agricultural University Beijing 100193 China Institute of Animal Sciences and Veterinary Medicine Zhejiang Academy of Agricultural Sciences Hangzhou 310021 China

The present study investigated the effects of fasting and refeeding on the expression of proteasorne-related genes and their downstream targets in the skeletal muscles of chicks. Seven-day-old chicks were fasted for 24 or 48 h and then refed for 4 h. The expression levels of MAFbx and MuRF1, which function as E3 ligases in the ubiquitin-proteasome system, were investigated at the mRNA and protein levels. MAFbx and MuRF1 expression were increased by fasting and these increases were downregulated by refeeding. The expression of the target proteins of these E3 ligases, MyoD and M-CK, was also analyzed. The levels of these proteins were downregulated by fasting, and these decreases were rescued by refeeding. The results of this study indicate that fasting stimulates MAFbx and MuRF1 expression in chicks, possibly leading to increased degradation of their corresponding target proteins.

关键词： fasting gene expression MAFbx MuRF1 MyoD M-CK

Genome-wide piggyBac transposon mediated screening reveals genes related to reprogramming

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Protein & Cell 2017年第2期8卷 134-139页

作者： Xi Zhang Xinglin Wei Yuanyuan Wu Yuzhe Wang Cheng Tan xiaoxiang hu Ning Li Mario R. Capecchi Sen Wu State Key Laboratory of Agrobiotechnology College of Biological Sciences China Agricultural University Beijing 100193 China Department of human Genetics University of Utah School of Medicine Salt Lake City UT 84112 USA

iPSCs are typically derived using four transcription factors Oct4 （also known as Pou5f1）, Klf4, Sox2 and c-Myc （OKSM）（Takahashi and Yamanaka, 2006）. Major directions in this field are focused on understanding the reprogramming mechanism, optimizing reprogramming methods to improve iPS cell （iPSC） quality, and applications of the cells for regenerative medicine.

关键词： transposon piggyBac Genome-wide