The isolation of gamones 3 and 4 of Euplotes octocarinatus

Gamones 3 and 4 of the ciliate Euplotes octocarinatus were isolated and purified to chromatographic and electrophoretic homogeneity. They are secreted into the culture medium by cells of certain mating types and induce cells of other mating types to unite in pairs and exchange gametic nuclei. The purified gamones are biologically active at concentrations as low as 0.1-1 pM. Both are polypeptides with unusually low pI values of approximately 3.2, and both have a carbohydrate content of less than 2%. Gamone 3 has an Mr of 18,800 and is slightly smaller than gamone 4, which has an Mr of 23,500. Gamone 3 was isolated from the starvation medium of cells homozygous for the mating type allele mt3 and gamone 4 was isolated from the medium of cells homozygous for the mating type allele mt4. Each of the two homozygous cell lines was found to secrete one gamone only.