title: Isolation and structural characterization of two water-borne pheromones from Euplotes crassus, a ciliate commonly known to carry membrane-bound pheromones.
abstract: Ciliates comprise species synthesizing water-diffusible mating type factors or pheromones and species synthesizing insoluble, cell membrane-bound pheromones. Euplotes crassus has traditionally been placed in the latter group. In contrast with this notion, we found that E. crassus is a constitutive pheromone-secreting ciliate, like other Euplotes species. From cell-free filtrate preparations of the E. crassus strain L-2D, we isolated two distinct pheromones, designated as Ec-α and Ec-1, and determined their complete amino acid sequences by combined chemical and genetic approaches. The Ec-α pheromone sequence extends for 56 amino acid residues with six cysteines and shows a molecular mass of 6,183 Da, while the Ec-1 pheromone sequence extends for 45 amino acid residues with 10 cysteines and shows a molecular mass of 4,840 Da. Marked structural differences distinguish the full-length Ec-α and Ec-1 coding sequences, which have been cloned and characterized from the transcriptionally active macronuclear genome. They were taken as clear indication that the Ec-α and Ec-1 pheromones are specified by genes that are not allelic, but likely derived from a duplicated genetic locus of the transcriptionally silent micronuclear genome.
authors.affiliation: Dipartimento di Scienze Ambientali e Naturali, University of Camerino, 62032 Camerino (MC), Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Alimenti
authors.forename: Adriana
authors.initials: A
authors.lastname: Vallesi
authors.forename: Sergio
authors.initials: S
authors.lastname: Federici
authors.forename: Graziano
authors.initials: G
authors.lastname: di Giuseppe
authors.forename: Dini
authors.initials: D
authors.lastname: Fernando
authors.forename: Vitale
authors.initials: V
authors.lastname: Carratore
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Luporini
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D016812:Euplotes / Q000254:growth & development / Q000378:metabolism*; D005374:Filtration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010675:Pheromones / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D014867:Water / Q000737:chemistry* / Q000469:parasitology*
chemical_list: D010675:Pheromones; D014867:Water