Hecht Oliver, Van Nuland Nico A, Schleinkofer Karin, Dingley Andrew J, Bruhn Heike, Leippe Matthias, Grötzinger Joachim
Biochemisches Institut der Christian-Albrechts-Universität Kiel, Olshausenstr. 40 24118 Kiel, Germany.
J Biol Chem. 2004 Apr 23;279(17):17834-41. doi: 10.1074/jbc.M312978200. Epub 2004 Feb 17.
Amoebapore A is a 77-residue protein from the protozoan parasite and human pathogen Entamoeba histolytica. Amoebapores lyse both bacteria and eukaryotic cells by pore formation and play a pivotal role in the destruction of host tissues during amoebiasis, one of the most life-threatening parasitic diseases. Amoebapore A belongs to the superfamily of saposin-like proteins that are characterized by a conserved disulfide bond pattern and a fold consisting of five helices. Membrane-permeabilizing effector molecules of mammalian lymphocytes such as porcine NK-lysin and the human granulysin share these structural attributes. Several mechanisms have been proposed to explain how saposin-like proteins form membrane pores. All mechanisms indicate that the surface charge distribution of these proteins is the basis of their membrane binding capacity and pore formation. Here, we have solved the structure of amoebapore A by NMR spectroscopy. We demonstrate that the specific activation step of amoebapore A depends on a pH-dependent dimerization event and is modulated by a surface-exposed histidine residue. Thus, histidine-mediated dimerization is the molecular switch for pore formation and reveals a novel activation mechanism of pore-forming toxins.
溶组织内阿米巴穿孔素A是一种由原生动物寄生虫和人类病原体溶组织内阿米巴产生的含77个氨基酸残基的蛋白质。溶组织内阿米巴穿孔素通过形成孔道来裂解细菌和真核细胞，在阿米巴病（最具生命威胁的寄生虫病之一）期间对宿主组织的破坏中起关键作用。溶组织内阿米巴穿孔素A属于类鞘脂激活蛋白样蛋白超家族，其特征是具有保守的二硫键模式和由五个螺旋组成的折叠结构。哺乳动物淋巴细胞的膜通透效应分子，如猪NK溶素和人类颗粒溶素，也具有这些结构特征。已经提出了几种机制来解释类鞘脂激活蛋白样蛋白如何形成膜孔。所有机制都表明，这些蛋白质的表面电荷分布是其膜结合能力和孔道形成的基础。在这里，我们通过核磁共振光谱法解析了溶组织内阿米巴穿孔素A的结构。我们证明，溶组织内阿米巴穿孔素A的特定激活步骤取决于pH依赖性二聚化事件，并受一个表面暴露的组氨酸残基调节。因此，组氨酸介导的二聚化是孔道形成的分子开关，并揭示了一种新型的成孔毒素激活机制。
