抗菌肽分子结构对其活性的影响

抗菌肽是一种广泛存在于生物界的抵抗病原微生物入侵的小分子多肽,是生物先天免疫的重要组成部分,具有广谱抗菌活性和抗肿瘤、抗病毒、抗真菌、抗寄生虫及免疫调节等生物活性,其区别于传统抗生素的独特作用机理,使其不易产生耐药性,是一类极具潜力的肽类抗生素.抗菌肽多样的分子结构是其产生生物活性的基础,研究表明抗菌肽的正电荷数、水脂两亲结构、保守序列、α-螺旋、二硫键、铰链结构和氨基酸构型对抗菌肽的活性至关重要.围绕以上几个方面对抗菌肽进行分子设计和改造,人们有望更加有效地提高抗菌肽的抗菌活性,获得到更加高效、低毒的抗菌肽产品.现就抗菌肽的分子结构以及结构对活性的影响等方而做一综述.     

抗菌肽的结构特征及其与活性的关系

抗菌肽是生物体内一类具有抗菌活性的多肽,是宿主非特异性防御系统的重要组成部分,广泛存在于自然界中,具有广谱的杀菌活性,其独特的生物学活性与其结构特征密切相关.文章简要介绍了抗菌肽的结构及其活性之间的关系,以期为设计新型抗菌肽分子,开发活性更高,抗菌谱更广的抗菌类药物提供理论依据.     

α、β多肽抗菌活性的定量构效关系研究

通过运用半经验计算方法对α和β两类抗菌肽的抗菌活性的定量构效关系研究，获得了两个相关性较好的线性回归方程。结果显示，α多肽的活性和键合能、溶剂可及面积、极化能、氧上最大负电荷相关；β多肽的活性和生成热、分子范德华面积、分子体积、极化能线性相关。logP对两类抗菌肽影响不大。在设计抗菌肽时，结构上应采用管状空间结构，性质上充分考虑其两性和两亲性，可采用正电性的赖氨酸或精氨酸与负电性的谷氨酸和天冬氨酸搭配；亲水性的丝氨酸或苏氨酸与疏水性苯丙氨酸、酪氨酸、色氨酸搭配，提高抗菌肽的活性。     

抗菌肽修饰方法与抗菌机制的研究进展

抗菌肽,是自然界中存在于众多生物体内对抗外源真菌、细菌及病毒等微生物入侵的天然防御系统主要活性成分.抗菌肽表现出较广的抗菌谱,抗菌机制独特且复杂,不易产生耐药性,被认为是目前多重耐药菌的较佳药物.许多非人源的抗菌肽有免疫原性、溶血反应及半衰期短等问题.研究工作者在原有的抗菌肽基础上,通过不同的修饰,使得抗菌肽的活性提高、毒性降低、制备工艺简化等.同时也有科研工作者,不断进行抗菌肽作用机制的研究,以期为抗菌肽的发现及设计提供更多的可行性借鉴.本文就近三年来,抗菌肽修饰及作用机制的研究进行综述.     

肽类抗生素对细胞选择性作用研究进展

抗菌肽是一种广泛存在于生物界的抵抗病原微生物入侵的重要防御分子。抗菌肽具有广谱抗细菌、真菌、肿瘤细胞等活性，具有自身随着物种适应环境而产生的结构多样性以及具有区别于传统抗生素的杀菌机理的独特性，是一类极有潜力的肽类抗生素。不同抗菌肽对不同类型靶细胞表现出活性上的巨大差异，即是抗菌肽作用的选择性，这种作用的选择性受到多种因素的影响。探讨抗菌肽作用细胞的机理，特别是选择性作用的机理将有助于设计出活性更高的新型肽类抗生素。本文主要从细胞表面结构特异性、抗菌肽自身结构特点阐述近年来抗菌肽活性与选择性作用研究的新进展。     

膜活性多肽(MAPs)的抗菌活性及其作用机制的研究进展

膜活性多肽(MAPs)是一类具有较好抗菌活性的抗菌肽。作为先天宿主防御分子,广泛的分布于细菌、植物、无脊椎动物、脊椎动物中。膜活性多肽具有抗菌肽的结构特征,肽链通常较短,带正电荷,具有两亲性的α-螺旋或β-折叠结构,通过破坏膜的通透性杀死细菌、真菌和部分肿瘤细胞。膜活性多肽在细胞膜或细胞内部存在特定的分子靶点,并因其独特的作用机制而成为一种新型的肽类抗生素。本文主要对膜活性多肽的抗菌活性及其作用机制的研究现状和发展情况做一综述。     

Lantibiotic:一类新颖的抗菌肽研究进展

lantibiotic是革兰氏阳性菌产生的抗菌肽,因其结构中含有羊毛硫氨酸（lanthionine),成为一类独特的抗革兰氏阳性菌的物质,乳链菌肽是研究最为清楚的lantibiotic类抗菌肽,介绍了其三维结构,生物学活性,细胞膜作用的分子机制（肽与细胞膜结合,插入细胞膜,细胞膜渗漏）及药用价值,并对lantibiotic类抗菌肽的作用模型进行了概述。     

阳离子抗菌肽的研究进展

阳离子抗菌肽是一类具抗微生物活性的小分子多肽，按结构特征可分为α－螺旋肽和β－折叠肽，不同来源或同一抗菌肽的不同结构形式生物活性差别较大，部分抗菌肽之间或抗菌肽与抗生素之间存在协同作用，特别是最近发现一些抗菌肽具有抗内毒素活性。阳离子抗菌肽的结构特征是其发挥作用的重要基础，α－螺旋肽通过其两亲性的α－螺旋上的正电茶与细菌细胞膜磷脂分子的负电荷之间的静电吸引而结合在细菌膜上，并借助于疏水段分子中连接结构的柔性插入到细胞膜中，最终通过膜内分子间的相互位移使抗菌肽分子相互聚集在一起形成离子通道，使细菌失去膜势，不能保持正常的渗透压而死亡。一般认为β－折叠肽也是和细胞膜结合后，结构发生变化而发挥作用。抗菌肽和细胞膜结合及形成离子通道受多种因素的影响，如阳离子抗菌肽的结构、浓度，环境 pH、温度，介质的离子强度。阳离子抗菌肽杀菌力强，抗菌谱广，不良反应少，因此在食品、农业，特别是在医药领域都有很好的应用前景，极可能发展成为一类全新的抗生素。     

两栖类皮肤抗菌肽的分离纯化与抗菌活性检测技术

两栖类皮肤抗菌肽由于具有广谱、高效的抗菌活性,且不引起微生物耐药性等特点,已成为目前开发新型抗菌药物的理想材料。文章概述了两栖类抗菌肽的主要特点及其分离纯化和抗菌活性检测的主要方法,并对这些技术的原理、方法及其近年来在抗菌肽研究中的进展进行了介绍。同时本文还比较了各种方法的优缺点,对当前研究中所存在的一些问题进行了初步的探讨,以期为两栖类抗菌肽的应用提供理论依据。     

人内源性抗菌肽的多样性研究

目的　从人单个核白细胞和子宫颈及子宫内膜粘液酸溶性提取物中分离纯化新的抗菌肽。方法　电泳凝胶琼脂糖弥散法分析 r IL- 2刺激培养的人单个核白细胞和子宫颈及子宫内膜粘液酸溶性提取物抗菌组分 ,用制备性酸性尿素聚丙烯酰胺凝胶电泳初步分离并制备电泳纯的各抗菌组分 ,反相高压液相色谱技术进一步纯化 ,琼脂糖弥散法分析其抗菌活性 ,Tricine- SDS- PAGE鉴定其纯度和分子量 ,用 Edman降解法进行氨基酸序列测定。结果　从刺激培养的人单个核白细胞分别纯化出 HL P- 2 / 2 3、HL P- 3/ 2 1两个抗菌肽分子 ,分子量分别是 7.84和 16 .86 ku;从子宫颈粘液及子宫内膜粘液分别分离纯化出 HCP- 1/ 2 1、HUP1/ 38两个抗菌肽分子 ,分子量分别为 13.89和 5 .95 ku。测定 HL P- 3/ 2 1分子的前 10位 N端氨基酸序列为PKRKAEGDAK。结论　人体抗菌肽分子存在多样性 ,HL P- 2 / 2 3、HL P- 3/ 2 1、HCP- 1/ 2 1和 HU P1/ 38可能为新的抗菌肽分子     

Antimicrobial Activity Developed by Scorpion Venoms and Its Peptide Component

Microbial infections represent a problem of great importance at the public health level, with a high rate of morbidity-mortality worldwide. However, treating the different diseases generated by microorganisms requires a gradual increase in acquired resistance when applying or using them against various antibiotic therapies. Resistance is caused by various molecular mechanisms of microorganisms, thus reducing their effectiveness. Consequently, there is a need to search for new opportunities through natural sources with antimicrobial activity. One alternative is using peptides present in different scorpion venoms, specifically from the Buthidae family. Different peptides with biological activity in microorganisms have been characterized as preventing their growth or inhibiting their replication. Therefore, they represent an alternative to be used in the design and development of new-generation antimicrobial drugs in different types of microorganisms, such as bacteria, fungi, viruses, and parasites. Essential aspects for its disclosure, as shown in this review, are the studies carried out on different types of peptides in scorpion venoms with activity against pathogenic microorganisms, highlighting their high therapeutic potential.     

Design of potent, non-toxic anticancer peptides based on the structure of the antimicrobial peptide, temporin-1CEa

Recent advances in the search for novel anticancer agents have indicated that the positively charged antimicrobial peptides have emerged as promising agents offering several advantages over the conventional anticancer drugs. As a naturally occurring, cationic, α-helical antimicrobial peptide, temproin-1CEa has been proved to exhibit a potent anticancer effect and a moderate hemolytic activity. In order to reduce the hemolytic activity of temporin-1CEa and improve its anticancer potency towards a range of human breast cancer cells, in the present study, six analogs of temporin-1CEa were rationally designed and synthesized. The amphipathicity levels and α-helical structural patterns of peptides were reserved, while their cationic property and hydrophobicity were changed. The results of MTT and hemolysis assay indicated that the analog peptides displayed an improved anticancer activity and showed an overall optimized therapeutic index. The hydrophobicity of peptides was positively correlated with their hemolytic and antitumor activities. Moreover, the data suggest a strategy of increasing the cationicity while maintaining the moderate hydrophobicity of naturally occurring amphipathic α-helical peptides to generate analogs with improved cytotoxicity against tumor cells but decreased activity against non-neoplastic cells such as human erythrocytes. This work highlights the potential for rational design and synthesis of improved antimicrobial peptides that have the capability to be used therapeutically for treatment of cancers.     

Alignment-based design and synthesis of new antimicrobial Aurein-derived peptides with improved activity against Gram-negative bacteria and evaluation of their toxicity on human cells

Considering the worldwide increasing prevalence of resistance to traditional antibiotics, it is necessary to find new antibiotics to deal with this issue. Recently, antimicrobial peptides (AMPs) have been proposed as new antimicrobial agents. Aureins are a family of AMPs that are isolated from Green and Golden Bell Frogs. These peptides have a favorable antibacterial activity against Gram-positive bacteria. We designed two peptides derived from natural Aurein enjoying alignment-based design method. After synthesis of the peptides, their secondary structure was checked by circular dichroism. Consequently, the antibacterial effects of these peptides were investigated by determining the minimum inhibitory concentration (MIC) and bactericidal concentration. Eventually, the toxicity of these peptides was determined by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay on normal human skin cells (Hu02 cell line). Natural Aurein1.2 was used as a natural control to compare the properties in all stages. The results indicated that these new peptides had medium-upward antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis (MIC of 8–64 μg/mL) and weak bactericidal activity against Staphylococcus aureus (MIC of 128–256 μg/mL). Also, MTT assays results showed that AureinN2 is less toxic than AureinN1 and Aurein1.2. Toxicity of AureinN2 for Hu02 cell lines was between 20 and 40% at the concentration of 8–500 μg/mL. In this study, we were able to improve antimicrobial activity of two synthetic derivatives of the Aurein family against Gram-negative bacteria by using machine-learning algorithm and other in silico methods.     

鲎源抗菌肽的制备及药用价值研究进展*

鲎源抗菌肽是一类来源于海洋珍贵的药源生物鲎血淋巴内的具有抗菌活性的多肽物质，在鲎天然免疫中起到至关重要的作用，它对外源病原菌的抗菌作用，降低了鲎自身的致病性，增强了鲎的天然免疫能力。鲎源抗菌肽与其他来源的抗菌肽相比有许多优势。现对鲎源抗菌肽的生物活性、分子结构、基因序列以及制备方法进行综述，并对其潜在药用价值进行了论述。     

Design and characterization of short hybrid antimicrobial peptides from pEM‐2, mastoparan‐VT1, and mastoparan‐B

Antimicrobial peptides are considered to be excellent templates for designing novel antibiotics because of their broad‐spectrum antimicrobial activity and their low prognostic to induce antibiotic resistance. In this study, for the first time, a series of short hybrid antimicrobial peptides combined by different fragments of venom‐derived alpha‐helical antimicrobial peptides pEM‐2, mastoparan‐VT1, and mastoparan‐B were designed with the intent to improve the therapeutic index of the parental peptides. Short hybrid antimicrobial peptides PV, derived from pEM‐2 and mastoparan‐VT1, was found to possess the highest antibacterial, hemolytic, and cytotoxic activity. Short hybrid antimicrobial peptides PV3, derived from pEM‐2 and three fragments of mastoparan‐VT1, showed more than threefold improvement in therapeutic index compared with parental peptides pEM‐2 and mastoparan‐VT1. PV had the highest antimicrobial activity in stability studies. Except BVP, designed based on all three parental peptides, the other short hybrid antimicrobial peptides at their minimal inhibitory concentration and 2× minimal inhibitory concentration required less than 120 and 60 min to reduce >3log10 the initial inoculum, respectively. All peptides had membrane‐disrupting activity in a time‐dependent manner. Collectively, this study highlights the potential for rational design of improved short hybrid antimicrobial peptides such as PV3 that was an ideal candidate for further assessment with the ultimate purpose of development of effective antimicrobial agents.     

Characterisation of antibacterial activity of peptides isolated from the venom of the spider Cupiennius salei (Araneae: Ctenidae).

The characterisation of the antimicrobial activity of five antibacterial peptides, isolated from the venom of the neotropical wandering spider Cupiennius salei is reported here. The peptides have a molecular mass, determined by electrospray ionisation-mass spectrometry, between 3-4 kDa. Minimal inhibitory concentrations against five different bacteria species were determined by a liquid growth inhibition assay. All five peptides showed minimal inhibitory concentrations that are comparable to those of other known antibacterial peptides, like insect defensins and cecropins, found in the last years in a large diversity of animals. The peptides are supposed to lyse the cells by formation of either distinct channels or pores, but their mode of action is not yet revealed.     

Design and synthesis of amphipathic antimicrobial peptides

A large proportion of antimicrobial peptides share a common structural feature that is critical to their antimicrobial activity, i.e. amphipathic α-helices. The amphipathy of a polypeptide chain can be quantitated through the value of the hydrophobic moment. Generally, antimicrobial peptides are characterized by high hydrophobic moment and low hydrophobicity values. Using these criteria we have identified two short segments that possess hydrophobic moment properties associated with known antimicrobial peptides. Using in vitro assays the segment derived from the protein perforin displays no antifungal or antibacterial activity and, while showing no α-helicity in buffer or liposomes, exhibits a modest degree of α-helical structure in the presence of the a-helical inducer, 2,2,2-trifluoroethanol. However, rational modifications result in a derivative which assumes an α-helical conformation in the presence of liposomes, exhibits potent antifungal activity against plant fungal pathogens, has significant antibacterial activity, effects leakage of a fluorescent dye from acidic liposomes and is devoid of hemolytic activity. Results are also presented for a segment derived from the human immunodeficiency virus envelope protein. We suggest that the identification of putative amphipathic structures in proteins may provide a useful starting strategy in the design and synthesis of antimicrobial peptides.     

Antimicrobial activities of human beta-defensins against Bacillus species

Natural defences in the human body function to protect us from numerous environmental toxins and exposure to potential harmful biological agents. An important frontline defence is antimicrobial peptides. These peptides occur at environmental interfaces and serve to limit bacterial invasion. There has been little work comparing specific peptides as potential antimicrobial compounds. In this study, we evaluated the antimicrobial activity of peptides from the human beta-defensin (HBD) family against four species of Bacillus, chosen as models for Bacillus anthracis, a potential bioweapon. The impact of peptide concentration, sequence and protein binding was evaluated on their biological activity. The results indicated that HBD-3 was the most biologically active against Bacillus subtilis and Bacillus licheniformis, whilst HBD-2 was found to be most active against Bacillus cereus and Bacillus thuringiensis. Moreover, the antimicrobial activity of the peptides was directly related to peptide concentration and indirectly related to albumin concentration (i.e. protein binding).