Keohane E M, Weiss L M
Department of Pathology, Albert Einstein College of Medicine, Bronx, N.Y. 10461, USA.
Folia Parasitol (Praha). 1998;45(2):117-27.
Microsporidia are eukaryotic, obligate intracellular organisms defined by their small spores containing a single polar tube that coils around the interior of the spore. After appropriate stimuli the germination of spores occurs. Conditions that promote germination vary widely among species, presumably reflecting the organism's adaptation to their host and external environment as well as preventing accidental discharge in the environment. It appears that calcium may be a key ion in this process. Regardless of the stimuli required for activation, all microsporidia exhibit the same response to the stimuli, that is, increasing the intrasporal osmotic pressure. This results in an influx of water into the spore accompanied by swelling of the polaroplasts and posterior vacuole. The polar tube then discharges from the anterior pole of the spore in an explosive reaction and is thought to form a hollow tube by a process of eversion. If the polar tube is discharged next to a cell, it can pierce the cell and transfer the sporoplasm into this cell. Polar tubes resist dissociation in detergents and acids but dissociate in dithiothreitol. We have developed a method for the purification of polar tube proteins (PTPs) using differential extraction followed by reverse phase high performance liquid chromatography (HPLC). This method was used to purify for subsequent characterization PTPs from Glugea americanus, Encephalitozoon cuniculi, E. hellem and E. intestinalis. These proteins appear to be members of a protein family that demonstrate conserved characteristics in solubility, hydrophobicity, mass, proline content and immunologic epitopes. These characteristics are probably important in the function of this protein in its self assembly during the eversion of the polar tube and in providing elasticity and resiliency for sporoplasm passage.
微孢子虫是真核、专性细胞内生物，其特征是具有小孢子，小孢子内含有一根围绕孢子内部盘绕的极管。在适当刺激后，孢子会发生萌发。促进萌发的条件在不同物种间差异很大，这大概反映了该生物体对其宿主和外部环境的适应性，以及防止在环境中意外释放。似乎钙可能是这个过程中的关键离子。无论激活所需的刺激是什么，所有微孢子虫对刺激都表现出相同的反应，即增加孢子内渗透压。这导致水流入孢子，同时极质体和后液泡肿胀。然后极管以爆发性反应从孢子的前端排出，并被认为通过外翻过程形成中空管。如果极管在细胞旁边排出，它可以刺穿细胞并将孢子质转移到该细胞中。极管在洗涤剂和酸中能抗解离，但在二硫苏糖醇中会解离。我们开发了一种方法，通过差异提取，然后进行反相高效液相色谱（HPLC）来纯化极管蛋白（PTPs）。该方法用于从美洲格留虫、兔脑炎微孢子虫、海伦脑炎微孢子虫和肠道脑炎微孢子虫中纯化PTPs，以便后续进行表征。这些蛋白质似乎是一个蛋白质家族的成员，它们在溶解性、疏水性、质量、脯氨酸含量和免疫表位方面表现出保守特征。这些特征可能在极管外翻过程中该蛋白质的自我组装功能中很重要，并且在为孢子质通过提供弹性和韧性方面也很重要。
