抗菌肽及其重组表达系统研究进展

抗菌肽作为一类具有多种生物学功能的小肽,具有分子量小、不含外源成分、不易产生耐药性等特性,成为近年来的研究热点。该文综述了抗菌肽的种类、作用机制及其重组表达系统等方面的研究进展,并对存在的热点问题进行了探讨。     

降血压肽基因工程菌的构建及高效表达策略

降血压肽具有很好的降血压效果而且天然无毒副作用,是目前基因工程研究的热点之一。本文阐述了降血压肽基因工程菌构建的重要性,综述了国内外关于降血压肽及各种小肽表达方面的研究进展。探讨了降血压肽基因工程菌在构建过程中目的片段的选择、串联连接的方式、串联体的获得及表达载体的选择等方面采用的策略和依据,重点介绍了各种不同表达类型载体的优缺点。旨在能对今后做降血压基因工程菌的多肽表达提供参考,以方便实验设计。     

类橡胶蛋白AbAMP1的重组表达及其抑菌活性研究

将类橡胶蛋白AbAMP1基因克隆至pPIC9,获得重组载体pPIC9-Ab,线性化后转化Pichia pastoris SMD1163,筛选获得阳性转化子.取表型为Mut*的转化子AS16进行诱导表达,上清经Tricine-SDS-PAGE分析,在约4.7 kD处有一条较强主带,与AbAMP1的预期大小相符,表明获得高效表达.上清经酸性非变性电泳后,用凝胶琼脂糖弥散法测定其抑菌活性,在含Bacillus thuringiensis琼脂糖平板AbAMP1对应处有一明显抑菌带,说明重组表达的AbAMP1具有天然活性.上清液抑菌活性试验显示,AbAMP1对Fusarium oxysporum f.sp.cubense以及B.thuringiensis,B.subtilis,Staphylococcus aureus等G 细菌均有显著的抑制作用,而对其它供试丝状真菌、酵母菌以及G-细菌无明显抑制作用.     

Study on Antiviral Activity of Two Recombinant Antimicrobial Peptides Against Tobacco Mosaic Virus

Probiotics and Antimicrobial Proteins - Antimicrobial peptides (AMPs) are generally small peptides with less than 50 amino acid residues, which have been considered as the first line of defense...     

抗菌肽Cec4a的重组表达和抗菌活性研究*

目的:构建Cec4a的原核重组表达体系,通过诱导表达、酶切纯化获得重组蛋白,并检测产物的抗菌活性。方法:基于Cec4a的序列设计引物,克隆Cec4a基因的DNA片段。利用原核表达载体(pCold-SUMO)构建重组原核表达质粒,并将其转化到大肠杆菌C41(DE3)等感受态细胞,使用IPTG进行诱导表达。通过Ni-NTA亲和层析柱纯化,获得含有His-SUMO标签的重组Cec4a融合蛋白。在SUMO蛋白酶酶切后,再次使用Ni-NTA亲和层析纯化,得到目的蛋白,最后用鲍曼不动杆菌(ATCC19606)作为指示菌检测表达产物的抗菌活性。结果:成功构建pCold-SUMO-Cec4a原核表达质粒,测序分析其序列与预期结果一致。Cec4a融合蛋白表达量为42.8mg/L,纯化后的Cec4a重组蛋白对鲍曼不动杆菌的MIC为4 μg/mL。结论:通过原核表达,并经Ni-NTA亲和层析纯化,获得了具有抗菌活性的重组蛋白Cec4a,为研究Cec4a的生物活性、抗菌机制及应用奠定了基础。     

Evaluation the Therapeutic Index of Recombinant Antimicrobial S3 Tetramer-Peptides Expressed in E. coli

International Journal of Peptide Research and Therapeutics - There is still a long way to go to commercialize antimicrobial peptides (AMPs) due to critical issues like efficiency, safety, and...     

Comparing Selection on S. aureus between Antimicrobial Peptides and Common Antibiotics

With a diminishing number of effective antibiotics, there has been interest in developing antimicrobial peptides (AMPs) as drugs. However, any new drug faces potential bacterial resistance evolution. Here, we experimentally compare resistance evolution in Staphylococcus aureus selected by three AMPs (from mammals, amphibians and insects), a combination of two AMPs, and two antibiotics: the powerful last-resort vancomycin and the classic streptomycin. We find that resistance evolves readily against single AMPs and against streptomycin, with no detectable fitness cost. However the response to selection from our combination of AMPs led to extinction, in a fashion qualitatively similar to vancomycin. This is consistent with the hypothesis that simultaneous release of multiple AMPs during immune responses is a factor which constrains evolution of AMP resistant pathogens.     

新疆家蚕抗菌肽抗菌作用的超微结构观察及抗菌机理初探

为探讨基因工程表达的新疆家蚕(Bombyx mori)抗菌肽(cecropin-XJ)的抗菌机制,通过紫外分光光度法研究抗菌肽的抑菌动力学,并采用透射电镜观察抗菌肽作用于金黄色葡萄球菌(Staphylococcus aureus)后的超微结构,对抗菌肽抗菌机理进行初步探讨。结果表明,抗菌肽抑菌作用比较明显,抗菌肽的活性与作用时间有关。抗菌肽可能是通过"桶-板"模式渗透细胞膜,从而影响细胞膜的结构和功能,使细胞膜形成许多孔道,增强了金黄色葡萄球菌细胞的通透性,造成细胞内的原生质扩散,并从孔道向胞外渗漏,影响了细菌的代谢系统,从而起到抑菌、杀菌作用。抗菌肽使金黄色葡萄球菌细胞内容物大量渗漏而死亡,死亡细胞的细胞壁保持完整,表明细胞膜是抗菌肽作用的主要靶位点。     

Synthetic Antimicrobial Peptides: I. Antimicrobial Activity of Amphiphilic and Nonamphiphilic Cationic Peptides

Comparative antimicrobial properties of three artificial cationic synthetic antimicrobial peptides (SAMP): (RAhaR)₄AhaβA (where R is Arg, Aha is 6-aminohexanoic acid, βA is beta-alanine), (KFF)₃K and R₉F₂ with various amphiphilic properties have been studied relative to pathogenic strains of microorganisms: Gram-negative bacteria Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis, and Salmonella enterica, Gram-positive bacteria Staphylococcus aureus, and pathogenic yeast fungus Candida albicans. The selectivity index (SI) values of the peptide preparations were calculated as the ratio of the 50% cytotoxic concentration (TC₅₀) towards eukaryotic host cells to the MIC₅₀ values of the testing antimicrobial peptides. The studied SAMPs appeared to be the most active against the pathogenic yeast fungus C. albicans and the bacterial strains St. aureus and P. aeruginosa. The SI values in these cases exceed 40. Some assumed molecular interactions of the studied SAMPs on the microbial cells have been considered, and possible pathways to increase their antimicrobial activity have been suggested. The proposed SAMPs can serve as a basis for the design and synthesis of new promising synthetic antimicrobial agents.     

Cholesterol Inhibition of Isopentenyl Pyrophosphate Δ3,Δ2-Isomerase in Mycoplasma laidlawii

Cholesterol inhibits isopentenyl Delta(3),Delta(2)-isomerase of Mycoplasma laidlawii in an apparently competitive fashion. The conversion of mevalonic acid to isopentenyl pyrophosphate is slightly stimulated. Organisms grown in the presence of mevalonic-2-(14)C acid contain small amounts of radio-label in nucleic acid and protein fractions. Most of the label is found in the lipids and is reduced dramatically in organisms grown with cholesterol. No significant accumulation of phosphorylated intermediates of polyterpene biosynthesis was observed in cells or culture supernatant fluid. All of the radioactivity appearing in the nucleic acid fraction occurs in the minor nucleoside, isopentenyl adenosine, of the transfer ribonucleic acid. The necessity for synthesis by the organisms of this minor nucleoside from mevalonic acid may explain the site of enzyme inhibition by cholesterol of polyterpene biosynthesis.     

Effect of Flexible and Rigid Linkers on Biological Activity of Recombinant Tetramer Variants of S3 Antimicrobial Peptide

International Journal of Peptide Research and Therapeutics - Antimicrobial peptides (AMPs) mainly introduced as a new generation of antibiotics, could be used for broad medical and biotechnological...     

Chloride-Inducible Expression Vector for Delivery of Antimicrobial Peptides Targeting Antibiotic-Resistant Enterococcus faecium

Antibiotic-resistant enterococcal infections are a major concern in hospitals where patients with compromised immunity are readily infected. Enterococcus faecium bacteria are of particular interest as these pathogens account for over 80% of vancomycin-resistant enterococcal infections. Antimicrobial peptides (AMPs) produced at the site of infection by engineered bacteria may offer a potential alternative to traditional antibiotics for the treatment of resistant bacteria such as E. faecium. For this mode of delivery to be effective, it is essential to identify a suitable protein expression system that can be used in the desired delivery bacterium. In this study, we describe a promising chloride-inducible promoter and its application in the bacterial delivery of AMPs from Lactococcus lactis to reduce counts of E. faecium bacteria in vitro. Reporter gene studies show that at chloride concentrations found within the human intestines, the chloride-inducible promoter exhibits high levels of protein expression compared to those of the commonly used nisin-inducible promoter. These results indicate that this system is powerful and would not require the exogenous administration of an inducer molecule. In its application for AMP production against E. faecium in vitro, L. lactis producing AMPs under the chloride promoter rapidly decreased E. faecium counts by nearly 10,000-fold. As an extension of this application, we also demonstrate the potential in using this type of delivery system in combination with traditional antibiotics to slow the development of resistance. Collectively, this study shows the promise of using a chloride-inducible promoter for the bacterial delivery of AMPs in the body for the treatment of vancomycin-resistant enterococci (VRE) and other antibiotic-resistant bacteria.     

毕赤酵母表达系统优化策略概述

毕赤酵母(Pichia pastor)表达系统是近年发展起来的一种高效表达外源蛋白的系统,利用该系统表达外源基因具有良好的应用前景。尽管毕赤酵母表达系统具有比较完备的基因表达调控机制和对真核基因表达产物的加工修饰能力,但由于基因本身及表达系统等诸多因素,仍然存在外源蛋白表达产量很低甚至不表达的情况。针对毕赤酵母表达系统这一因素,对表达载体的优化,毕赤酵母菌株优化及发酵条件优化进行了综述,以期为外源基因在毕赤酵母中的高效表达提供理论基础。     

杂合抗菌肽在毕赤酵母中的表达及其活性测定

为获得溶血活性低、抗菌活性高的杂合抗菌肽,以家蝇抗菌肽Cec Md和中国林蛙抗菌肽Chensirin为母体肽,并结合毕赤酵母偏爱密码子的原则,设计出6条具有抗菌潜力的新型杂合抗菌肽,将其命名为CC22、CC28、CC29、CC30和CC34(1),CC34,利用SOE-PCR技术合成所需的目的基因,并将其克隆至毕赤酵母表达载体pGAPZαA,通过电击转化技术,将其转化至毕赤酵母SMD1168中,经含有Zeocin的抗性平板筛选阳性转化子,YPD液体培养72h后,经Tricine-SDS-PAGE检测出目的蛋白,然后采用高效液相色谱法对其进行纯化。检测结果显示,表达产物CC29对大肠杆菌、鸡沙门氏菌的最小抑菌浓度(MIC)均为25μg/ml;CC34(1)对大肠杆菌表现相对较弱的抑制作用,最小抑菌浓度为100μg/ml;CC34对鸡沙门氏菌和金黄色葡萄球菌的最小抑菌浓度为50μg/ml;且杂合抗菌肽对有益菌均没有表现出抑制作用。6条杂合肽的溶血活性均呈现较低水平,其中表现出抗菌活性的3条抗菌肽中,以CC29的溶血活性最低,CC34(1)和CC34相对次之。结合抑菌活性,CC29和CC34的抑菌效果较为明显,从而确定溶血活性低且抗菌活性较高的CC29和CC34为新型杂合抗菌肽。     

Synthesis and Biological Evaluation of Gramicidin S‐Inspired Cyclic Mixed α/β‐Peptides

Via a Mannich reaction involving a dibenzyliminium species and the titanium enolates of Evans' chiral acylated oxazolidinones the β²‐amino acids (R)‐ and (S)‐Fmoc‐β²homovaline and (R)‐Fmoc‐β²homoleucine are synthesized. These building blocks were used, in combination with commercially available α‐ and β³‐amino acids, for the synthesis of the cyclo‐(αβ³αβ²α)₂ peptide 2 and the cyclo‐(αβ²αβ³α)₂ peptides 3 – 5 . The peptides 2 – 5 were screened for their ability to inhibit a small panel of Gram‐negative and Gram‐positive bacterial strains.     

抗菌肽的设计及其应用

抗菌肽(AMP)是生物体内先天免疫系统的一个组成部分,保护机体免受致病微生物的入侵.抗菌肽具有很强的广谱抗菌活性,可抑制革兰氏阳性菌、革兰氏阴性菌、真菌和病毒的生长.为克服微生物对抗生素耐药性的问题,目前阳离子抗菌肽已被考虑作为抗生素的潜在替代品.本文将阐述抗菌肽的作用机理、选择性抗菌肽的设计及其应用.     

Direct Expression of Antimicrobial Peptides in an Intact Form by a Translationally Coupled Two-Cistron Expression System

We describe a novel prokaryotic expression system for the production of cationic antimicrobial peptides (AMPs). The method relies on a translationally coupled two-cistron system, in which the termination codon for the first cistron (which encodes the anionic polypeptide mIFc2, a derivative of human gamma interferon) overlaps with the initiation codon for the second cistron (which encodes a cationic AMP) in the sequence of 5′-TAATG-3′. By forming an insoluble complex with the AMP upon translation, the mIFc2 protein efficiently neutralized the toxicity of the coexpressed cationic AMP and minimized the sensitivity of AMP to proteolytic degradation in a host. The AMPs were retrieved from the insoluble inclusion bodies without any chemical or enzymatic cleavage step by simple cation-exchange chromatography. With our system, ∼100 mg of various AMPs (buforin IIb, parasin I, and pexiganan) were obtained from 1 liter of Escherichia coli culture. Our expression system may represent a universal cost-effective solution for the mass production of intact AMPs in their natural forms.Of worldwide concern is the increasing development of bacterial and fungal strains that are resistant to currently available antimicrobial drugs. This worsening situation has spurred Herculean efforts to develop new classes of antibiotics with novel targets and modes of action (19). Cationic antimicrobial peptides (AMPs) play a key role in the primary host defense of living organisms against infections by pathogenic microorganisms. Because their mechanisms of antimicrobial action differ from those of conventional antibiotics, AMPs have received increasing attention as a potential new class of therapeutic substances (22, 30).In contrast to bacterial growth in the presence of commonly prescribed antibiotics, the growth of bacteria in the presence of AMPs does not easily give rise to the selection of pathogenic drug-resistant mutant strains. This is because AMPs rapidly kill microbes by a variety of mechanisms, including (i) fatal depolarization of the normally energized bacterial membrane, (ii) creation of physical holes that cause cellular contents to leak out, (iii) degradation of the cell wall, (iv) disturbance of membrane functions, and/or (v) damaging of critical intracellular targets after internalization of the AMPs (7, 11, 19, 22, 30). Moreover, AMPs activate the host''s innate (nonspecific) immune response without acting as a foreign antigen target of the host''s adaptive immune system (23, 30). Despite the fact that AMPs show great potential as a novel class of antibiotics, the lack of a cost-effective means of mass production has limited the development of these peptides as human therapeutics (8).Numerous biological expression systems have been introduced for the cost-effective production of AMPs in Escherichia coli (9). To decrease their natural destructive behavior toward microorganisms and sensitivity to proteolytic degradation, AMPs are often produced as fusion proteins in heterologous hosts (12, 16). These studies show that certain fusion partner proteins neutralize the toxicity of AMPs and improve their stability against proteolysis in an expression host. In another series of experiments, recombinant AMP-containing fusion proteins are expressed in tandem repeats in an attempt to increase AMP production. As expected, multimeric expression further enhanced the yield of AMP fusion proteins (9, 12, 16). However, all of these methods require that the AMP be separated from its fusion partner, and recombinant fusion proteins, including multimeric ones, are usually cleaved with enzymes such as furin or chemicals such as CNBr (12, 16). This additional process results in inefficient cleavage and thus poor recovery of AMPs from fusion partners. Moreover, unwanted amino acid residue(s) are often included in the AMPs after the cleavage reaction and can decrease antimicrobial activity and cause problematic side effects (18). Therefore, a new approach for producing an intact and biologically active AMP without the inclusion of an enzymatic or chemical cleavage step is needed.We have developed here a novel translationally coupled, two-cistron expression system for the production of recombinant AMPs in their natural forms. Using this system, we were able to produce, from 1 liter of E. coli culture, ∼100 mg of a potent AMP, buforin IIb (BIIb) (15), without a cleavage step, and other cationic AMPs (parasin I [24] and pexiganan [6]) were also successfully produced.     

昆虫抗菌肽研究和应用现状

昆虫在受到刺激或感染之后,在其血淋巴中会产生一种抗菌类物质,称抗菌肽。抗菌肽具有分子小、稳定性好、广谱抗菌、无毒副作用等特点,在农业、医药、食品等领域有广泛的应用前景。简要综述了昆虫抗菌肽的基础研究和应用现状。     

两栖动物皮肤结构及皮肤抗菌肽

两栖动物皮肤在自然进化过程中形成了防御病原微生物的三套防御系统,相应地具有特定结构。皮肤抗菌肽是其中先天性防御系统的主要组成部分。本文概述了两栖动物皮肤结构特点以及皮肤抗菌肽在国内外的最新研究进展,重点介绍了两栖动物皮肤腺体和蛙皮抗菌肽的种类、分子结构、抗菌机理、基因表达调控及cDNA编码特点以及基因工程等。以期系统认识和了解这些方面的研究与进展。     

Rapid Screening of Antimicrobial Synthetic Peptides

Increasing resistance to conventional antibiotics among microorganisms is one of the leading problems of medicine nowadays. Antimicrobial peptides are compounds exhibiting both antibacterial and antifungal activities. However, it is difficult to predict whether a designed new compound would exhibit any biological activity. Moreover, purification of the peptides is one of the most time-consuming and expensive steps of the synthesis that sometimes leads to unnecessary loss of solvents and reagents. In our study we have developed a thin-layer chromatography (TLC) direct bioautography technique for rapid determination of antimicrobial activity of peptides without the necessity of high-performance liquid chromatography purification. In this assay, crude peptides were applied and separated on a TLC plate. Then, pre-prepared plates were dipped into microbial suspension and incubated under optimum conditions for bacteria and fungi as well. The activity of the tested compounds was visualized by spraying the TLC plates with a cell viability reagent, resazurin (7-hydroxy-3H-phenoxazin-3-one 10-oxide). Effectiveness of this assay was compared with minimal inhibitory concentration results obtained by broth microdilution assay. Interestingly, so far such a screening method has not been applied for this group of compounds.