舟山黄海葵兴奋性毒素AX-1的分离纯化及鉴定

目的从舟山黄海葵(AnthopLeura xanthogrammica)的刺细胞中分离纯化多肽类毒素分子并进行功能鉴定。方法通过反复冻融法以及多步高效液相色谱分离技术从舟山黄海葵毒素中分离到一种新型多肽类毒素,进行质谱鉴定和三维结构模拟,并运用膜片钳技术检测海葵毒素多肽对大鼠背根神经节(DRG)细胞的河豚毒素-敏感型(TTX-S)和河豚毒素-不敏感型(TTX-R)钠离子通道的影响。结果获得由48个氨基酸组成,相对分子质量为5018.2的多肽毒素分子,命名为AX-1,含3对二硫键;三维结构模拟表明该毒素多肽的结构以反平行β-折叠片以及loop结构为主,该毒素能抑制大鼠背根神经节细胞的钠离子通道的失活并显著增加钠离子通道的电流。结论AX-1是一种兴奋性多肽毒素,可作为潜在的强心肽药物。     

天然芋螺毒素肽的化学合成

芋螺毒素是由热带海洋肉食性软体动物芋螺分泌的、富含二硫键的一类结构多样的小分子多肽。芋螺毒素的化学合成已成为获得毒素肽的主要手段。现总结化学合成芋螺毒素线性肽及其氧化折叠形成二硫键的多种方法 ,并对现阶段化学合成芋螺毒素肽的新进展加以综述。     

胱氨酸/谷氨酸反向转运体作为药物靶点的研究进展

胱氨酸/谷氨酸反向转运体[system Xc(-)]是一种不依赖钠离子的氨基酸转运蛋白,由轻链亚基xCT和重链亚基4F2hc (CD98)通过二硫键组成的异二聚体。System Xc(-)主要通过介导胱氨酸摄取与谷氨酸的输出,维持细胞内外谷氨酸、胱氨酸和半胱氨酸的平衡,调控膜内外谷氨酸的水平及胞内谷胱甘肽的合成,从而对氧化应激和谷氨酸神经毒性产生影响。本文对system Xc(-)的结构、功能进行阐述,分析该转运体在生理和病理中的作用,讨论其在不同疾病中的作用及机制,探讨system Xc(-)作为药物靶点的具体研究进展。本文通过对system Xc(-)的研究现状进行总结,为进一步深入研究system Xc(-)及药物的研发提供理论指导。     

缺失错配修复基因MLH1的结直肠癌HCT唱116细胞对氟尿嘧啶耐药机制的研究

目的 研究缺失错配修复基因MLH1（MutL homolog 1）的结直肠癌细胞HCT-116对氟尿嘧啶（5-Fu）耐药机制。方法 通过构建MLH1缺失的结直肠癌细胞HCT-116稳定表达MLH1细胞株,CCK-8试剂检测细胞恢复MLH1表达后对化疗药物5-Fu耐药性的影响,并通过流式细胞仪检测细胞表面干细胞标志CD133和分化标志CK20以及CK8的表达变化。结果 HCT-116稳定表达MLH1分子后,其对5-Fu作用的化疗耐受性降低,5-Fu处理后细胞的活率显著降低（P<0.01）;流式细胞仪检测结果显示CD133表达显著降低,并伴随细胞分化标志CK8和CK20表达上调。结论 结直肠癌细胞缺失错配修复基因MLH1引起5-Fu耐药性可能与其促进肿瘤干细胞样特性密切相关。     

重组人纽兰格林二硫键分析

目的：应用多种质谱技术确证重组人纽兰格林（rhNRGL）的一级结构及其二硫键定位。方法：（1）利用Q—FT—MS测定rhNRGL二硫键还原前后的精确相对分子质量，确定分子中二硫键数目；（2）应用MALDI—TOF／TOF—MS法测定rhNRGL的N端序列；（3）用ESI-MS／MS法测定rhNRGL的C端序列；（4）通过Trypsin和Glu—C2种蛋白酶进行酶解，获得肽质量指纹谱，确证其序列及定位3对二硫键。结果：（1）测定rhNRGL还原前后的精确相对分子质量，两者相差6．0516，确证其主成分形成了3对二硫键；（2）串联质谱法测定rhNRGL的N端序列的5个氨基酸和C端序列的11个氨基酸，均与理论序列一致；（3）2种酶切肽谱的序列覆盖率分别为82％和64％，分析确证主成分二硫键配对正确，但同时存在少量错配二硫键异构体。结论：以上结果表明，该样品的一级结构正确，主要二硫键模式为：1—3，2—4，5—6。多肽药物的二硫键分析常常需要多种质谱及样品制备技术联合。     

多肽抗生素研究进展

多肽抗生素是生物界中广泛存在的一类生物活性小肽 ,一般具有抗细菌或真菌的作用 ,有些还具有抗原虫、病毒或癌细胞的功能。按照化学结构的不同 ,多肽抗生素可分为5类 :①具有螺旋结构的线性多肽 ;②富含某种氨基酸的线性多肽 ;③含有一个二硫键的多肽 ;④含有两个或两个以上二硫键的多肽 ;⑤羊毛硫抗生素。根据作用机理的不同 ,多肽抗生素又可分为裂解细胞膜的裂解肽和非裂解肽。多肽抗生素已经开始用于医药、食品和植物抗病基因工程等方面 ,并且有着很大的发展潜力。     

串联质谱法在合成多肽药物结构确证中的应用进展

目的:综述串联质谱法在合成多肽药物结构表征方面的应用进展,为该类药物的结构表征提供方法参考。方法:以"合成多肽药物""多肽测序""串联质谱""质谱法""结构确证""Synthetic polypeptide drugs""Peptide sequencing""Tandem mass spectrometry""Mass spectrometry""Structure interpretation study"等为关键词,组合查询了2000年1月-2019年1月中国知网、万方、维普、Springer Link、Web of Science、PubMed等数据库中的相关文献,对串联质谱法应用于确证合成多肽类药物结构的研究进展进行归纳与总结。结果与结论:共检索到相关文献192篇,其中有效文献52篇。合成多肽药物主要由氨基酸构成,这类药物在结构确证研究方面与一般药物有所不同。根据目前相关技术指导原则以及有关文献研究,合成多肽药物结构表征的主要内容包括分子量测定、氨基酸组成和序列分析、二硫键分析以及二级结构分析等。近年来,串联质谱法及其与其他方法的结合在合成多肽药物结构确证中应用广泛,成为Edman降解多肽测序法的有效补充,且其因灵敏度高、分析速度快、所需样品量少等优点,已成为确证多肽药物结构的有力工具。     

芋螺毒素的研究进展

芋螺毒素（conotoxin,CTx)是一类具有神经药理活性的多肽。由于芋螺毒素的多样性而成为新的进化选择性物质的组合库。芋螺毒素富含二硫键,具有作用于神经系统内的分子,尤其是一些配体和电压门控离子通道,因而在药学方面具有极其重要的价值。据称它们可与植物类的生物碱媲美,也可与微生物发酵产品匹敌。本文按CTx作用的受体靶分别进行综述。     

利用高分辨质谱技术综合解析胰岛素类制品复杂二硫键结构

二硫键的正确配对维持了多肽和蛋白类药物的正确折叠方式和高级结构的形成,对产品的质量控制至关重要。为了确保二硫键正确配对,二硫键分析是多肽和蛋白质药物表征中必不可少的重要部分。质谱分析技术可用于二硫键分析,然而,胰岛素及其类似物中存在两对没有酶切位点的二硫键,常规的碰撞诱导解离(CID)和高能诱导裂解(HCD)无法实现该复杂二硫键的准确定位。本研究通过3种方法综合定位该复杂二硫键,包括酶切加关键肽段源内碎裂(ISD)法、酶切加部分还原烷基化法、完整蛋白源内碎裂和电子转移解离(ETD)裂解法,并且考察了门冬胰岛素、赖脯胰岛素和甘精胰岛素的适用性,为胰岛素及其类似物二硫键连接方式的质量控制提供了新途径,也为含该类复杂二硫键多肽或蛋白类生物制品的二硫键定位提供借鉴。     

芋螺毒素B179的化学合成及其氧化折叠的研究

目的合成新型芋螺毒素B179,并对其氧化折叠进行研究。方法采用Fmoc固相合成法合成芋螺毒素多肽B179,研究了不同的氧化缓冲液、谷胱甘肽浓度、还原型与氧化型谷胱甘肽的比例、以及温度对氧化折叠的影响。结果采用Fmoc固相合成法可以成功合成线性肽,其氧化折叠产物中主要为含一对二硫键的产物,但还出现了其他副产物,可能是含有分子间二硫键的折叠产物;在高浓度还原型谷胱甘肽环境下,折叠副产物更易形成;随着氧化反应温度升高,折叠反应速率加快。结论固相合成法可以有效合成芋螺毒素B179,且不同因素对其二硫键的形成有着较大的影响,本研究结果可为新型芋螺毒素的合成及其氧化折叠提供借鉴。     

Potential therapeutic applications of the cyclotides and related cystine knot mini-proteins

Cyclotides are naturally occurring mini-proteins that have a cyclic peptide backbone and a knotted arrangement of three disulfide bonds. They are remarkably stable and have a diverse range of therapeutically useful biological activities, including antimicrobial and anti-HIV activity, although their natural function appears to be as plant defence agents. Cyclotides are amenable to chemical synthesis and the potential exists to graft new bioactivities onto their cyclic cystine knot framework as a way of stabilising peptide drugs. Over the last few years, proof-of-concept that bioactive peptide epitopes can be grafted onto cyclotides and related cystine knot mini-proteins has been obtained. The cystine knot framework is tolerant to a wide range of residue substitutions and is showing great promise as a scaffold in drug design and protein engineering.     

The cystine knot motif in toxins and implications for drug design.

The cystine knot structural motif is present in peptides and proteins from a variety of species, including fungi, plants, marine molluscs, insects and spiders. It comprises an embedded ring formed by two disulfide bonds and their connecting backbone segments which is threaded by a third disulfide bond. It is invariably associated with nearby beta-sheet structure and appears to be a highly efficient motif for structure stabilization. Because of this stability it makes an ideal framework for molecular engineering applications. In this review we summarize the main structural features of the cystine knot motif, focussing on toxin molecules containing either the inhibitor cystine knot or the cyclic cystine knot. Peptides containing these motifs are 26-48 residues long and include ion channel blockers, haemolytic agents, as well as molecules having antiviral and antibacterial activities. The stability of peptide toxins containing the cystine knot motif, their range of bioactivities and their unique structural scaffold can be harnessed for molecular engineering applications and in drug design. Applications of cystine knot molecules for the treatment of pain, and their potential use in antiviral and antibacterial applications are described.     

Potential therapeutic applications of the cyclotides and related cystine knot mini-proteins

Cyclotides are naturally occurring mini-proteins that have a cyclic peptide backbone and a knotted arrangement of three disulfide bonds. They are remarkably stable and have a diverse range of therapeutically useful biological activities, including antimicrobial and anti-HIV activity, although their natural function appears to be as plant defence agents. Cyclotides are amenable to chemical synthesis and the potential exists to graft new bioactivities onto their cyclic cystine knot framework as a way of stabilising peptide drugs. Over the last few years, proof-of-concept that bioactive peptide epitopes can be grafted onto cyclotides and related cystine knot mini-proteins has been obtained. The cystine knot framework is tolerant to a wide range of residue substitutions and is showing great promise as a scaffold in drug design and protein engineering.     

Host-defense activities of cyclotides

Cyclotides are plant mini-proteins whose natural function is thought to be to protect plants from pest or pathogens, particularly insect pests. They are approximately 30 amino acids in size and are characterized by a cyclic peptide backbone and a cystine knot arrangement of three conserved disulfide bonds. This article provides an overview of the reported pesticidal or toxic activities of cyclotides, discusses a possible common mechanism of action involving disruption of biological membranes in pest species, and describes methods that can be used to produce cyclotides for potential applications as novel pesticidal agents.     

Stability and Safety of Inhibitor Cystine Knot Peptide,GTx1-15, from the Tarantula Spider Grammostola rosea

Inhibitor cystine knot (ICK) peptides are knotted peptides with three intramolecular disulfide bonds that affect several types of ion channels. Some are proteolytically stable and are promising scaffolds for drug development. GTx1-15 is an ICK peptide that inhibits the voltage-dependent calcium channel Ca_v3.1 and the voltage-dependent sodium channels Na_v1.3 and Na_v1.7. As a model molecule to develop an ICK peptide drug, we investigated several important pharmaceutical characteristics of GTx1-15. The stability of GTx1-15 in rat and human blood plasma was examined, and no GTx1-15 degradation was observed in either rat or human blood plasma for 24 h in vitro. GTx1-15 in blood circulation was detected for several hours after intravenous and intramuscular administration, indicating high stability in plasma. The thermal stability of GTx1-15 as examined by high thermal incubation and protein thermal shift assays indicated that GTx1-15 possesses high heat stability. The cytotoxicity and immunogenicity of GTx1-15 were examined using the human monocytic leukemia cell line THP-1. GTx1-15 showed no cytotoxicity or immunogenicity even at high concentrations. These results indicate that GTx1-15 itself is suitable for peptide drug development and as a peptide library scaffold.     

Cyclotides as a basis for drug design

Introduction: Cyclotides are plant-made defence proteins with a head-to-tail cyclic backbone combined with a conserved, six cystine knot. They have a range of biological activities, including uterotonic and anti-HIV activity, which have attracted attention to their potential pharmaceutical applications. Furthermore, their unique structures and high stability make them appealing as peptide-based templates for drug design applications. Methods have been developed for their production, including solid phase peptide synthesis as well as recombinant methods.

Areas covered: This article reviews the recent literature associated with therapeutic applications of naturally occurring and synthetically modified cyclotides. It includes applications of cyclotides and cyclotide-like molecules as peptide-based drug leads and diagnostic agents.

Expert opinion: The ultra-stable cyclotides are promising templates for drug development applications and are currently being assessed for the potential breadth of their applications. For synthetic versions of cyclotides to enter human clinical trials further studies to examine their biopharmaceutical properties and toxicities are required. However, several promising proof-of-concept studies have established that pharmaceutically relevant bioactive peptide sequences can be grafted into cyclotide frameworks and thereby stabilised, while maintaining biological activity. These studies include examples directed at cancer, cardiovascular disease and infectious diseases. Solid phase peptide synthesis has been the preferred approach for making pharmaceutically modified cyclotides so far, but promising progress is being made in biological approaches to cyclotide production.     

Two novel sodium channel inhibitors from Heriaeus melloteei spider venom differentially interacting with mammalian channel's isoforms

Two new polypeptide toxins named Hm-1 and Hm-2 were isolated from the venom of the crab spider Heriaeus melloteei. These toxins consist of 37 and 40 amino acid residues, respectively, contain three intramolecular disulfide bonds, and presumably adopt the inhibitor cystine knot motif. Hm-1 is C-terminally amidated and shows a low degree of homology to spider toxins agelenin and mu-agatoxin-II, whereas Hm-2 has no relevantly related peptide sequences. Hm-1 and Hm-2 were found to act on mammalian voltage-gated Na(+) channels. Both toxins caused a strong decrease of Na(+) current peak amplitude, with IC(50) values of 336.4 and 154.8nM, respectively, on Na(V)1.4. Hm-1 and Hm-2 did not shift the voltage-dependence of activation, nor did they change the kinetics of fast inactivation of the Na(+) currents. Interestingly, both toxins negatively shifted the steady-state inactivation process, which might have important functional consequences in vivo. However, this hyperpolarizing shift cannot by itself explain the observed inhibition of the Na(+) current, indicating that the two presented toxins could provide important structural information about the interaction of polypeptide inhibitors with voltage-gated Na(+) channels.     

Insecticidal plant cyclotides and related cystine knot toxins.

Cyclotides are small disulphide-rich peptides found in plants from the violet (Violaceae), coffee (Rubiaceae) and cucurbit (Cucurbitaceae) families. They have the distinguishing structural features of a macrocyclic peptide backbone and a cystine knot made up of six conserved cysteine residues, which makes cyclotides exceptionally stable. Individual plants express a suite of cyclotides in a wide range of tissue types, including leaves, flowers, stems and roots and it is thought that their natural function in plants is as defence agents. This proposal is supported by their high expression levels in plants and their toxic and growth retardant activity in feeding trials against Helicoverpa spp. insect pests. This review describes the structures and activities of cyclotides with specific reference to their insecticidal activity and compares them with structurally similar cystine knot proteins from peas (Pisum sativum) and an amaranthus crop plant (Amaranthus hypocondriancus). More broadly, cystine knot proteins are common in a wide range of organisms from fungi to mammals, and it appears that this interesting structural motif has evolved independently in different organisms as a stable protein framework that has a variety of biological functions.     

Cyclotides: a patent review

INTRODUCTION: Cyclotides are bioactive mini-proteins from plants that have the unique topological feature of a head-to-tail cyclic backbone combined with a cystine knot. Because of this structure they are ultra-stable and have attracted interest as peptide-based templates for drug design applications. Cyclotide biosynthesis involves processing from a genetically encoded precursor protein but methods have been developed for their man-made synthesis using solid phase peptide synthesis as well as recombinant methods. Their natural function in plants is as insecticidal agents and thus they have potential applications in agriculture. However, they have a range of pharmaceutically relevant activities, including anti-HIV, antimicrobial and uterotonic activity. Their exceptional stability and facile synthesis lend them to uses as pharmaceutical templates into which bioactive peptide sequences can be grafted. AREAS COVERED: This article reviews the patent literature associated with cyclotides with a focus on therapeutic applications. These patents are primarily related to the use of cystine knot scaffolds for the production of peptide-based drug leads, molecular probes or diagnostic agents. EXPERT OPINION: Although no cyclotide-related peptide has yet reached clinical trials, proof-of-concept has been obtained that bioactive peptide sequences can be grafted onto a cyclotide framework, maintaining biological activity while becoming resistant to proteolysis. Thus, cyclotides are promising templates in drug development applications and there is increasing interest in them and related cystine knot scaffolds, as well as in the use of other disulfide-rich scaffolds, in drug design.     

The Cystine Knot Is Responsible for the Exceptional Stability of the Insecticidal Spider Toxin ω-Hexatoxin-Hv1a

The inhibitor cystine knot (ICK) is an unusual three-disulfide architecture in which one of the disulfide bonds bisects a loop formed by the two other disulfide bridges and the intervening sections of the protein backbone. Peptides containing an ICK motif are frequently considered to have high levels of thermal, chemical and enzymatic stability due to cross-bracing provided by the disulfide bonds. Experimental studies supporting this contention are rare, in particular for spider-venom toxins, which represent the largest diversity of ICK peptides. We used ω-hexatoxin-Hv1a (Hv1a), an insecticidal toxin from the deadly Australian funnel-web spider, as a model system to examine the contribution of the cystine knot to the stability of ICK peptides. We show that Hv1a is highly stable when subjected to temperatures up to 75 °C, pH values as low as 1, and various organic solvents. Moreover, Hv1a was highly resistant to digestion by proteinase K and when incubated in insect hemolymph and human plasma. We demonstrate that the ICK motif is essential for the remarkable stability of Hv1a, with the peptide’s stability being dramatically reduced when the disulfide bonds are eliminated. Thus, this study demonstrates that the ICK motif significantly enhances the chemical and thermal stability of spider-venom peptides and provides them with a high level of protease resistance. This study also provides guidance to the conditions under which Hv1a could be stored and deployed as a bioinsecticide.