Identification of a biochemical marker for the secretory pathway in Tetrahymena thermophila

Tetrahymena thermophila is a ciliated protozoan studied by investigators from a wide range of disciplines as a model system for a variety of specialized eukaryoticcell functions. The proteinaceous secretory products of T thermophila have been isolated and characterized [1] and in this study we identify the major secretory product, a 34,000 Mr polypeptide, and use an antiserum prepared against this secretory protein to (1) demonstrate that this 34,000 Mr polypeptide is truly a secreted protein in Tetrahymena and (2) monitor the synthesis and transport of this protein by indirect immunofluorescence and light microscopy during mucocyst biogenesis.