Gruber Christian W, Cemazar Masa, Anderson Marilyn A, Craik David J
Institute for Molecular Bioscience and Australian Research Council Special Research Centre for Functional and Applied Genomics, University of Queensland, Brisbane, Queensland, 4072, Australia.
Toxicon. 2007 Mar 15;49(4):561-75. doi: 10.1016/j.toxicon.2006.11.018. Epub 2006 Nov 30.
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.
环肽是一类富含二硫键的小分子肽，存在于堇菜科、茜草科和葫芦科植物中。它们具有大环肽主链和由六个保守半胱氨酸残基组成的胱氨酸结这一独特的结构特征，这使得环肽异常稳定。单个植物在包括叶、花、茎和根在内的多种组织类型中表达一系列环肽，人们认为它们在植物中的天然功能是作为防御因子。这一观点得到了它们在植物中的高表达水平以及在针对棉铃虫等害虫的喂食试验中的毒性和生长抑制活性的支持。本综述描述了环肽的结构和活性，特别提及了它们的杀虫活性，并将它们与来自豌豆（Pisum sativum）和一种苋科作物（Amaranthus hypocondriancus）的结构相似的胱氨酸结蛋白进行了比较。更广泛地说，胱氨酸结蛋白在从真菌到哺乳动物的广泛生物体中都很常见，而且这种有趣的结构基序似乎在不同生物体中独立进化，成为具有多种生物学功能的稳定蛋白质框架。
