Species-specific aggregation factor in sponges. IV. Inactivation of the aggregation factor by mucoid cells from another species.

The role of protein synthesis in the cell union was investigated in conjugation of Blepharisma intermedium. In order to avoid possible complications due to the occurrence of other processes in conjugation, the homotypic cell union, in which conjugation is arrested at the stage of cell union without further changes, was used. Such unions were induced by treating cells of one mating type with the gamone of the other mating type for about 2 h. The induction of cell union was regularly accompanied by increased protein synthesis, which started 5 min after the beginning of the gamone treatment and continued for about 2 h. When protein synthesis was inhibited by cycloheximide, cell union was also inhibited. The extent of the two inhibitions were closely correlated. We concluded that gamone induces proteins and that protein synthesis is essential for cell union. Proteins synthesized in gamone-treated and non-treated cells were also separated and compared. Consideration of these results leads to a hypothesis that most of the gamone-induced proteins are membrane proteins normally synthesized, though in lesser amount, in non-conjugating cells and that cells gain the capacity to unite when these proteins are accumulated at a restricted area on the cell surface by another gamone-controlled mechanism.