人乳铁蛋白肽的分子改良及在大肠杆菌中的表达研究

采用SOE-PCR技术,设计合成hLF18-40的编码基因;以融合表达策略构建了pET-43.1a-hLF18-40表达质粒,并获得较高的可溶融合蛋白表达;将融合蛋白Nus-hLF18-40进行Ni2+柱亲和层析、除盐、浓缩后,用肠激酶切割释放抗茵肽hLF18-40,为今后基因工程法表达人乳铁蛋白肽提供了依据.同时,将...     

重组人乳铁蛋白基因克隆及表达

目的　构建重组人乳铁蛋白 (HLF)的毕赤酵母分泌表达菌株 ,并对表达产物进行评价。方法　由外周血白细胞总RNA经RT- PCR克隆获得HLF基因结构cDNA ,测序后克隆入酵母表达载体获得质粒pPIC9K- HLF ,线性化后电转化入毕赤酵母 ,经G4 -18 YPD筛选多拷贝后进行甲醇诱导表达。结果　获得基因与GenBank中的人HLF0 1基因基本相符。 2株多拷贝菌株诱导表达产物均能与人HLF抗体反应 ,具有抑制大肠杆菌生长的作用。结论　获得了能分泌有活性HLF的重组人乳铁蛋白 (HLF)的毕赤酵母分泌表达菌株。     

丝状真菌异源蛋白高效表达的研究进展

丝状真菌作为细胞工厂在生物技术领域被广泛应用于生产药物、化学试剂和酶类。近年来,丝状真菌基因组学领域取得了快速发展,利用丝状真菌表达异源蛋白也越来越受到重视。本文从基因表达与调控、蛋白质分泌途径及丝状真菌菌株等方面对丝状真菌高效表达异源蛋白的最新研究进展作一综述。     

乳铁蛋白纯化和检测方法研究进展

乳铁蛋白是一种具有抗微生物活性的铁离子结合糖蛋白,属于转铁蛋白家族的一员,具有调节炎症反应和激活免疫系统等功能,因此乳铁蛋白被广泛应用于医学和食品领域。本综述汇集了乳铁蛋白纯化和检测方法的研究进展,并比较了各方法之间的优缺点。     

乳铁蛋白介导的肺靶向纳米脂质载体的研究进展

纳米脂质载体属纳米给药体系,是在固体脂质纳米粒基础上发展起来的新型靶向给药系统,以生物相容性好的固态和液态脂质混合作为载体材料,将药物包裹于类脂核中,具有胶体载体如脂质体和纳米乳的优势,可用作抗肿瘤药物的靶向载体,同时,相比而言,纳米脂质载体雾化稳定性更好,在气道中具有良好的耐受性和理想的肺沉积率,适用于雾化吸入给药,该给药方式可使药物直达病灶,雾滴长时间滞留在肿瘤部位,发挥长效作用。为进一步提高药物的生物利用度、增强肺癌靶向性,可用乳铁蛋白对纳米脂质载体进行表面修饰。乳铁蛋白属转铁蛋白家族,正常肺组织中转铁蛋白受体呈阴性或低表达,而在非小细胞肺癌中转铁蛋白的阳性表达率远远高于正常肺组织,存在过度表达现象,可利用乳铁蛋白作为配体修饰纳米脂质载体,通过转铁蛋白介导的方式增加药物在肺癌细胞内的富集,受体介导的内吞可以进一步促进负载药物的纳米脂质载体的细胞摄取。     

乳铁蛋白纯化方法的优化

将纯度为50%左右的乳铁蛋白溶液加入带羧甲基的弱酸性阳离子交换剂CM-Sepharose Fast Flow进行动态吸附,采用质量分数为1.6%和5%的NaCl溶液进行阶跃洗脱;并对层析过程和接样方法进行了优化.结果表明,经过重复层析和优化方法接样,乳铁蛋白纯度可达96.7%.     

牛乳铁蛋白肽在酿酒酵母中的分泌表达及其活性

目的在酿酒酵母中分泌表达牛乳铁蛋白肽(bovine lactoferricin,LfcinB),并检测其活性。方法根据LfcinB的氨基酸序列,按照酿酒酵母密码子偏好性设计LfcinB基因序列,人工合成LfcinB基因,扩增后插入质粒pYES2-α中,构建重组表达质粒pYES2-α-LfcinB,转化至酿酒酵母INVSc1中,半乳糖诱导表达。采用抗生素微生物效价测定法中的管碟法一剂量法检测表达的LfcinB对大肠埃希菌DH5α和枯草杆菌的抑菌活性。对重组酵母菌的诱导时间、诱导剂浓度和诱导温度进行优化,并检测重组LfcinB的稳定性。结果重组表达质粒pYES2-α-LfcinB经双酶切和测序证明构建正确;重组酵母菌诱导表达产物可见相对分子质量分别为5 164和4 355的特异蛋白条带,每升工程菌发酵液中目的蛋白含量约为2.878 5 mg;表达的重组LfcinB对大肠埃希菌DH5α和枯草杆菌均有明显的抑菌活性;在诱导温度为26℃、半乳糖浓度为3%的条件下诱导96 h时,LfcinB的抑菌活性最高;重组LfcinB具有热稳定性,且二硫键的存在对其抑菌活性无影响。结论已成功在酿酒酵母中分泌表达了具有活性的LfcinB,为进一步研究LfcinB的生物功能及其应用奠定了基础。     

牛乳铁蛋白十肽的基因改造、克隆及表达

目的克隆并表达牛乳铁蛋白十肽及其突变体M1和M2基因。方法参照大肠杆菌偏爱密码子,分别针对牛乳铁蛋白十肽及其突变体M1和M2基因,设计并合成两个具有相同黏性末端的DNA片段,同时在其基因前后分别加上天冬酰胺和甘氨酸的密码子,构成羟胺裂解位点,通过连接获得其二拷贝基因同向串联体。分别将该串联体克隆至载体pUC18上,经双酶切、PCR及测序鉴定后,构建重组表达质粒,转化大肠杆菌BL21(DE3),IPTG诱导表达。表达产物纯化后,用凝血酶切割及羟胺裂解。结果获得了牛乳铁蛋白十肽及其突变体M1和M2二拷贝基因,并在大肠杆菌BL21(DE3)中表达出相对分子质量约29000的目的蛋白条带,纯化后的蛋白经凝血酶切割后,相对分子质量约29000的目的蛋白条带消失。结论已成功克隆并表达了牛乳铁蛋白十肽及其突变体M1和M2基因,为基因工程抗真菌肽的制备奠定了基础。     

外源蛋白在大肠杆菌中的可溶性表达策略

长期以来,大肠杆菌一直是表达外源蛋白的首选表达系统. 但由于外源蛋白在表达过程中容易被宿主细胞蛋白酶降解或者形成包涵体,其应用受到了限制. 本文综述了在大肠杆菌中表达可溶外源蛋白的策略和进展,以期提高具有生物活性的外源基因的表达水平.     

Immunomodulatory Effect of Human Lactoferrin on Toll-like Receptors 2 Expression as Therapeutic Approach for Keratoconus

Keratoconus (KC) is a corneal disorder whose etiology shares a close relationship with Lactoferrin (LTF) dysregulation and Toll-like Receptors 2 (TLR2) overexpression. This study shows how these two important biomarkers are clinically and molecularly interrelated, increasing knowledge about KC pathophysiology, and opening the door to future therapies. In this prospective clinical study, serum and tear LTF concentrations were quantified in 90 KC patients and 60 controls. A correlation analysis with multiple blood and tear immunoinflammatory mediators, and KC-associated tomographic parameters, was performed. An in vitro study using HEK-Blue^TMhTLR2 cell cultures was also conducted to determine the expression and functionality of TLR2 under the influence of LTF treatment. As a result, a LTF decreased was observed in KC patients compared to controls (p < 0.0001), evidencing the strong correlation with TLR2 overexpression at systemic and ocular surface level, with inflammatory mediator upregulation and with KC severity. In stimulated cell cultures, TLR2 expression was decreased using 2 mg/mL of LTF. The levels of secreted embryonic alkaline phosphatase (SEAP) and interleukin-8 (IL-8) were also reduced in supernatants after LTF treatment. As conclusions, the dysregulation of LTF and TLR2 in the ocular surface of KC patients contributes to KC severity by maintaining a detrimental chronic immune–inflammatory state. The immunomodulatory properties of LTF on TLR2 expression suggest its potential as a therapeutic approach for KC.     

大肠杆菌体系外源蛋白表达速度的调控策略

介绍和评价了目前针对大肠杆菌体系外源蛋白表达的转录、翻译和折叠阶段的各种表达速度调控策略. 根据现有各类调控策略的作用阶段、特点及优缺点,提出对蛋白表达各步骤分别调节,从而获得合适的整体表达速度以优化表达效果,提高大肠杆菌体系外源蛋白生产效率和产品质量,进一步提高其适用性和经济性.     

Heterologous Expression and Structural Characterisation of a Pyrazinone Natural Product Assembly Line

Through a number of strategies nonribosomal peptide assembly lines give rise to a metabolic diversity not possible by ribosomal synthesis. One distinction within nonribosomal assembly is that products are elaborated on an enzyme‐tethered substrate, and their release is enzyme catalysed. Reductive release by NAD(P)H‐dependent catalysts is one observed nonribosomal termination and release strategy. Here we probed the selectivity of a terminal reductase domain by using a full‐length heterologously expressed nonribosomal peptide synthetase for the dipeptide aureusimine and were able to generate 17 new analogues. Further, we generated an X‐ray structure of aureusimine terminal reductase to gain insight into the structural details associated with this enzymatic domain.     

Generation of New Complestatin Analogues by Heterologous Expression of the Complestatin Biosynthetic Gene Cluster from Streptomyces chartreusis AN1542

The heterologous expression of the biosynthetic gene cluster (BGC) of natural products enables the production of complex metabolites in a well‐characterized host, and facilitates the generation of novel analogues by the manipulation of the genes. However, the BGCs of glycopeptides such as vancomycin, teicoplanin, and complestatin are usually too large to be directly cloned into a single cosmid. Here, we describe the heterologous expression of the complestatin BGC. The 54.5 kb cluster was fully reconstituted from two overlapping cosmids into one cosmid by λ‐RED recombination‐mediated assembly. Heterologous expression of the assembled gene cluster in Streptomyces lividans TK24 resulted in the production of complestatin. Deletion of cytochrome P450 monooxygenase genes (open reading frames 10 and 11) and heterologous expression of the modified clusters led to the production of two new monocyclic and linear derivatives, complestatins M55 and S56.     

Altered Phenotypes in Saccharomyces cerevisiae by Heterologous Expression of Basidiomycete Moniliophthora perniciosa SOD2 Gene

Heterologous expression of a putative manganese superoxide dismutase gene (SOD2) of the basidiomycete Moniliophthora perniciosa complemented the phenotypes of a Saccharomyces cerevisiae sod2Δ mutant. Sequence analysis of the cloned M. perniciosa cDNA revealed an open reading frame (ORF) coding for a 176 amino acid polypeptide with the typical metal-binding motifs of a SOD2 gene, named MpSOD2. Phylogenetic comparison with known manganese superoxide dismutases (MnSODs) located the protein of M. perniciosa (MpSod2p) in a clade with the basidiomycete fungi Coprinopsis cinerea and Laccaria bicolor. Haploid wild-type yeast transformants containing a single copy of MpSOD2 showed increased resistance phenotypes against oxidative stress-inducing hydrogen peroxide and paraquat, but had unaltered phenotype against ultraviolet–C (UVC) radiation. The same transformants exhibited high sensitivity against treatment with the pro-mutagen diethylnitrosamine (DEN) that requires oxidation to become an active mutagen/carcinogen. Absence of MpSOD2 in the yeast sod2Δ mutant led to DEN hyper-resistance while introduction of a single copy of this gene restored the yeast wild-type phenotype. The haploid yeast wild-type transformant containing two SOD2 gene copies, one from M. perniciosa and one from its own, exhibited DEN super-sensitivity. This transformant also showed enhanced growth at 37 °C on the non-fermentable carbon source lactate, indicating functional expression of MpSod2p. The pro-mutagen dihydroethidium (DHE)-based fluorescence assay monitored basal level of yeast cell oxidative stress. Compared to the wild type, the yeast sod2Δ mutant had a much higher level of intrinsic oxidative stress, which was reduced to wild type (WT) level by introduction of one copy of the MpSOD2 gene. Taken together our data indicates functional expression of MpSod2 protein in the yeast S. cerevisiae.     

Pacidamycin Biosynthesis: Identification and Heterologous Expression of the First Uridyl Peptide Antibiotic Gene Cluster

The pacidamycins are antimicrobial nucleoside antibiotics produced by Streptomyces coeruleorubidus that inhibit translocase I, an essential bacterial enzyme yet to be clinically targeted. The novel pacidamycin scaffold is composed of a pseudopeptide backbone linked by a unique exocyclic enamide to an atypical 3′‐deoxyuridine nucleoside. In addition, the peptidyl chain undergoes a double inversion caused by the incorporation of a diamino acid residue and a rare internal ureido moiety. The pacidamycin gene cluster was identified and sequenced, thereby providing the first example of a biosynthetic cluster for a member of the uridyl peptide family of antibiotics. Analysis of the 22 ORFs provided an insight into the biosynthesis of the unique structural features of the pacidamycins. Heterologous expression in Streptomyces lividans resulted in the production of pacidamycin D and the newly identified pacidamycin S, thus confirming the identity of the pacidamycin biosynthetic gene cluster. Identification of this cluster will enable the generation of new uridyl peptide antibiotics through combinatorial biosynthesis. The concise cluster will provide a useful model system through which to gain a fundamental understanding of the way in which nonribosomal peptide synthetases interact.     

Structural Diversification of Lyngbyatoxin A by Host‐Dependent Heterologous Expression of the tleABC Biosynthetic Gene Cluster

Natural products have enormous structural diversity, yet little is known about how such diversity is achieved in nature. Here we report the structural diversification of a cyanotoxin—lyngbyatoxin A—and its biosynthetic intermediates by heterologous expression of the Streptomyces‐derived tleABC biosynthetic gene cluster in three different Streptomyces hosts: S. lividans, S. albus, and S. avermitilis. Notably, the isolated lyngbyatoxin derivatives, including four new natural products, were biosynthesized by crosstalk between the heterologous tleABC gene cluster and the endogenous host enzymes. The simple strategy described here has expanded the structural diversity of lyngbyatoxin A and its biosynthetic intermediates, and provides opportunities for investigation of the currently underestimated hidden biosynthetic crosstalk.     

A Novel L-Asparaginase from Hyperthermophilic Archaeon Thermococcus sibiricus: Heterologous Expression and Characterization for Biotechnology Application

L-asparaginase (L-ASNase) is a vital enzyme with a broad range of applications in medicine and food industry. Drawbacks of current commercial L-ASNases stimulate the search for better-producing sources of the enzyme, and extremophiles are especially attractive in this view. In this study, a novel L-asparaginase originating from the hyperthermophilic archaeon Thermococcus sibiricus (TsA) was expressed in Escherichia coli, purified and characterized. The enzyme is optimally active at 90 °C and pH 9.0 with a specific activity of 2164 U/mg towards L-asparagine. Kinetic parameters K_M and V_max for the enzyme are 2.8 mM and 1200 µM/min, respectively. TsA is stable in urea solutions 0–6 M and displays no significant changes of the activity in the presence of metal ions Ni²⁺, Cu²⁺, Mg²⁺, Zn²⁺ and Ca²⁺ and EDTA added in concentrations 1 and 10 mmol/L except for Fe³⁺. The enzyme retains 86% of its initial activity after 20 min incubation at 90 °C, which should be enough to reduce acrylamide formation in foods processed at elevated temperatures. TsA displays strong cytotoxic activity toward cancer cell lines K562, A549 and Sk-Br-3, while normal human fibroblasts WI-38 are almost unsensitive to it. The enzyme seems to be a promising candidate for further investigation and biotechnology application.