title: Self-compatible B mutants in coprinus with altered pheromone-receptor specificities.
abstract: A successful mating in the mushroom Coprinus cinereus brings together a compatible complement of pheromones and G-protein-coupled receptors encoded by multiallelic genes at the B mating-type locus. Rare B gene mutations lead to constitutive activation of B-regulated development without the need for mating. Here we characterize a mutation that arose in the B6 locus and show that it generates a mutant receptor with a single amino acid substitution (R96H) at the intracellular end of transmembrane domain III. Using a heterologous yeast assay and synthetic pheromones we show that the mutation does not make the receptor constitutively active but permits it to respond inappropriately to a normally incompatible pheromone encoded within the same B6 locus. Parallel experiments carried out in Coprinus showed that a F67W substitution in this same pheromone enabled it to activate the normally incompatible wild-type receptor. Together, our experiments show that a single amino acid replacement in either pheromone or receptor can deregulate the specificity of ligand-receptor recognition and confer a self-compatible B phenotype. In addition, we use the yeast assay to demonstrate that different receptors and pheromones found at a single B locus belong to discrete subfamilies within which receptor activation cannot normally occur.
authors.affiliation: Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
authors.forename: N S
authors.initials: NS
authors.lastname: Olesnicky
authors.forename: A J
authors.initials: AJ
authors.lastname: Brown
authors.forename: Y
authors.initials: Y
authors.lastname: Honda
authors.forename: S L
authors.initials: SL
authors.lastname: Dyos
authors.forename: S J
authors.initials: SJ
authors.lastname: Dowell
authors.forename: L A
authors.initials: LA
authors.lastname: Casselton
mesh_terms: D000595:Amino Acid Sequence; D002628:Chemoreceptor Cells / Q000502:physiology*; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal / Q000235:genetics*; D003302:Coprinus / Q000235:genetics*; D003433:Crosses, Genetic; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D005816:Genetic Complementation Test; D016297:Mutagenesis, Site-Directed; D010675:Pheromones / Q000235:genetics; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D005656:Fungal Proteins; D010675:Pheromones; D011994:Recombinant Proteins