Purification and initial characterization of two pheromones from the marine Antarctic ciliate, Euplotes nobilii

Among a set of wild-type strains of Euplotes,nobilii, every one derived ase xually from one specimen isolated from Terra Nova Bay (Ross Sea, Antarctica ). two were found to be representative of different mating types mutually c apable of inducing each other to form mating pairs through pheromones const itutively secreted into the extracellular environment. Pheromones of strain AC-1 were purified to homogeneity and shown to be represented by two disti nct proteins, that were denoted En-1 and En-2. En-1, secreted in amounts th ree-fold greater than En-2, was determined to have a molecular weight of 56 17 and an asparagine at the N-terminus of its amino acid sequence, while En -2 has a molecular weight of 6290 and bears an asparctic acid at its N-term inus. The fact that En-1 and En-2 are coreleased by genetically identical c ells of the same strain was taken to imply that they carry a heterozygotic combination of allelic pheromone genes and that these genes are regulated b y relationships of co-dominance.