title: Coding genes and molecular structures of the diffusible signalling proteins (pheromones) of the polar ciliate, Euplotes nobilii.
abstract: In protozoan ciliates, diffusible signalling proteins (pheromones) regulate the vegetative growth and mating interactions. Here, the coding genes and the structures of the encoded pheromones were studied in genetically distinct wild-type strains representing interbreeding Antarctic and Arctic populations of the marine ciliate Euplotes nobilii. Determination of seven allelic pheromone-coding DNA sequences revealed that an unusual extension and high structural conservation of the 5' non-coding region are peculiar traits of this gene family, implying that this region is directly involved in the mechanism of pheromone gene expression, possibly through phenomena of intron splicing and/or frame-shifting. For four pheromones, the three-dimensional structures were determined by nuclear magnetic resonance spectroscopy in solution. These structures show that the pheromones represent a protein family which adapts to its polar environment by combining a structurally stable core of a three-helix bundle with extended polypeptide segments that are devoid of regular secondary structures and concomitantly show enhanced structural flexibility.
authors.affiliation: Dipartimento di Scienze Ambientali e Naturali, University of Camerino, 62032 Camerino-MC, Italy.
authors.forename: Adriana
authors.initials: A
authors.lastname: Vallesi
authors.forename: Claudio
authors.initials: C
authors.lastname: Alimenti
authors.forename: Bill
authors.initials: B
authors.lastname: Pedrini
authors.forename: Graziano
authors.initials: G
authors.lastname: Di Giuseppe
authors.forename: Fernando
authors.initials: F
authors.lastname: Dini
authors.forename: Kurt
authors.initials: K
authors.lastname: Wüthrich
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Luporini
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000864:Antarctic Regions; D001110:Arctic Regions; D001483:Base Sequence; D016812:Euplotes / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010675:Pheromones / Q000737:chemistry* / Q000235:genetics*; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics*
chemical_list: D010675:Pheromones; D015800:Protozoan Proteins