The extrusion apparatus of the microsporidian parasitic protozoan Nosema michaelis discharges an invasion (or polar) tube with a velocity suitalbe for piercing cells and injecting infective sporoplasm. The tube is composed of a polar tube protein (PTP) which consists of a single, low molecular weight polypeptide slightly smaller than chymotrypsinogen-A. Assembled PTP tubes resist dissociation in sodium dodecyl sulfate and brief exposures in media at extreme ends of the pH range; however, the tubes are reduced by mercaptoethanol and dithiothreitol. When acidified, mercaptoethanol-reduced PTP self-assembles into plastic, two-dimensional monolayers. Dithiothreitol-reduced PTP will not reassemble when acidified. Evidence is presented which indicates that PTP is assembled as a tube within the spore; that the ejected tube has plasticity during sporoplasm passage; and, finally, that the subunits within the tube polymer are bound together, in part, by interprotein disulfide linkages.
Article| October 01 1976
The microsporidian spore invasion tube. The ultrastructure, isolation, and characterization of the protein comprising the tube.
J Cell Biol (1976) 71 (1): 23–34.
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E Weidner; The microsporidian spore invasion tube. The ultrastructure, isolation, and characterization of the protein comprising the tube.. J Cell Biol 1 October 1976; 71 (1): 23–34. doi: https://doi.org/10.1083/jcb.71.1.23
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