Updated project metadata. This project is focused on isolation and characterization of polar tube proteins (PTPs) of Anncaliia algerae using diverse bioinformatic and experimental methodologies - from mass spectrometry to heterologous expression to antibody production and immunolocalization. A novel protein was isolated from A. algerae polar tube extracts named PTP6 which could participates in recognition of host cell receptors as well.Moreover the obtained data on immunolabeling of the polar tubes in the process of extrusion, strongly support one of three hypothetical mechanisms for spore firing, namely the “everting-like-a-glove finger” model. The practical result of this fundamental research is the elaboration of the novel workflow that allows identification and isolation of PTPs in a given microsporidian species wich unites different approaches, such as homology search, sporal protein extractions by thiol-reducing agents, antibody-based approaches, as well as a protocol for purification of extruded polar tubes combined with mass spectrometry to identify new polar tube components.