Department of Biology, Biotechnical faculty, University of Ljubljana, Vecna pot 111, 1000 Ljubljana, Slovenia.
Toxicon. 2009 Dec 15;54(8):1125-34. doi: 10.1016/j.toxicon.2009.02.026. Epub 2009 Mar 5.
Actinoporins are effective pore-forming toxins produced by sea anemones. These extremely potent, basic 20 kDa proteins readily form pores in membranes that contain sphingomyelin. Much has been learned about the molecular basis of their pore-forming mechanism in recent years. Pore formation is a multi-step process that involves recognition of membrane sphingomyelin, firm binding to the membrane accompanied by the transfer of the N-terminal region to the lipid-water interface and finally pore formation after oligomerisation of three to four monomers. The final conductive pathway is formed by amphipathic alpha-helices, hence actinoporins are an important example of so-called alpha-helical pore-forming toxins. Actinoporins have become useful model proteins to study protein-membrane interactions, specific recognition of lipids in the membrane, and protein oligomerisation in the lipid milieu. Recent sequence and structural data of proteins similar to actinoporins indicate that they are not a unique family restricted to sea anemones as was long believed. An AF domain superfamily (abbreviated from actinoporin-like proteins and fungal fruit-body lectins) was defined and shown to contain members from three animal and two plant phyla. On the basis of functional properties of some members we hypothesise that AF domain proteins are peripheral membrane proteins. Finally, ability of actinoporins to form transmembrane pores has been exploited in some novel biomedical applications.
肌动蛋白原是海葵产生的有效成孔毒素。这些极其有效的、碱性的 20 kDa 蛋白很容易在含有神经鞘磷脂的膜上形成孔。近年来，人们对其成孔机制的分子基础有了更多的了解。成孔是一个多步骤的过程，包括识别膜神经鞘磷脂、与膜的牢固结合，同时将 N 端区域转移到脂-水界面，最后在三到四个单体的寡聚化后形成孔。最终的导电途径是由两亲性的 α-螺旋形成的，因此肌动蛋白原是所谓的α-螺旋成孔毒素的一个重要例子。肌动蛋白原已成为研究蛋白质-膜相互作用、膜中脂质的特异性识别以及脂质环境中蛋白质寡聚化的有用模型蛋白。最近与肌动蛋白原相似的蛋白质的序列和结构数据表明，它们不是一个像以前认为的那样仅限于海葵的独特家族。定义了一个 AF 结构域超家族（来自肌动蛋白原样蛋白和真菌子实体凝集素的缩写），并表明该超家族包含来自三个动物门和两个植物门的成员。基于一些成员的功能特性，我们假设 AF 结构域蛋白是外周膜蛋白。最后，肌动蛋白原形成跨膜孔的能力已在一些新的生物医学应用中得到了利用。
