一種昆士蘭錐形蝸牛的毒液中深藏成千上萬種肽類毒素,，被證明含有珍貴藥物先導價值,，或可以提供治療疼痛和癌癥藥物的新線索,。在發(fā)表在PNAS上的這篇研究中，研究人員描述了一種分析毒液毒素結構的新方法,。
Paul Alewood是University of Queensland分子生物學的教授,，他表示說這項研究是第一次給出了存在于一個單一的錐形蝸牛毒液中的毒素。研究的這種錐形蝸牛名叫conus episcopatus,，生活在澳大利亞東海岸,，是700種不同錐形蝸牛之一。錐形蝸牛毒液混合有許多復雜化學物質,，而大部分的這些毒素在過去都被忽略了,。
錐形蝸牛特征在于有一個復雜精細的毒液“裝置”，負責生物合成和提供富含半胱氨酸毒素肽的復雜混合物。這些毒素折疊成小的高度結構化的框架（frameworks）,，使它們能夠強效和選擇性地與異源離子通道和受體相互作用,。
使用包含精確測量，分析結構,、活性和內毒液蛋白的各種不同組合物的新分析方法,，利用生物化學和生物信息學工具，研究人員發(fā)現在一個單一的錐形蝸牛毒素肽中表達量最多的一種,，擁有3305個新的前提毒素序列,。它含有藥理活性的C-C-CC-C-C的抑制劑胱氨酸結和CC-C-C的特征序列。更重要的是,，他們同時發(fā)現了六個原始的“框架”（三維形狀的分子）,，可以作為藥物前體。在過去的25年共有25個知名的框架結構被發(fā)現,，而其中諸多都已經引用到針對幾種疾病的藥物或藥物前體當中,。
研究人員估計他們新發(fā)現的框架結構也將導致新的藥物研發(fā)，可用于治療疼痛,、癌癥和一系列的其他疾病,。Alewood表示：“我們預計有很多有趣的分子將在其他物種的毒液被發(fā)現，我們渴望用我們新的方法來探索這些,。我們新發(fā)現的這種方法也可用在其他相關領域,，如從細胞中研究蛋白質的表達。這將有助于我們更好地理解生物學,，尋找疾病模式,，或發(fā)現潛在的新藥物。”
DOI: 10.1073/pnas.1501334112
PMC
PMID
Optimized deep-targeted proteotranscriptomic profiling reveals unexplored Conus toxin diversity and novel cysteine frameworks
Vincent Lavergne, Ivon Harliwong, Alun Jones, David Miller, Ryan J. Taft and Paul F. Alewood
Abstract
Cone snails are predatory marine gastropods characterized by a sophisticated venom apparatus responsible for the biosynthesis and delivery of complex mixtures of cysteine-rich toxin peptides. These conotoxins fold into small highly structured frameworks, allowing them to potently and selectively interact with heterologous ion channels and receptors. Approximately 2,000 toxins from an estimated number of >70,000 bioactive peptides have been identified in the genus Conus to date. Here, we describe a high-resolution interrogation of the transcriptomes (available at www.ddbj.nig.ac.jp) and proteomes of the diverse compartments of the Conus episcopatus venom apparatus. Using biochemical and bioinformatic tools, we found the highest number of conopeptides yet discovered in a single Conus specimen, with 3,305 novel precursor toxin sequences classified into 9 known superfamilies (A, I1, I2, M, O1, O2, S, T, Z), and identified 16 new superfamilies showing unique signal peptide signatures. We were also able to depict the largest population of venom peptides containing the pharmacologically active C-C-CC-C-C inhibitor cystine knot and CC-C-C motifs (168 and 44 toxins, respectively), as well as 208 new conotoxins displaying odd numbers of cysteine residues derived from known conotoxin motifs. importantly, six novel cysteine-rich frameworks were revealed which may have novel pharmacology. Finally, analyses of codon usage bias and RNA-editing processes of the conotoxin transcripts demonstrate a specific conservation of the cysteine skeleton at the nucleic acid level and provide new insights about the origin of sequence hypervariablity in mature toxin regions.
