Genetic approach to regulated exocytosis using functional complementation in Paramecium: identification of the ND7 gene required for membrane fusion.
Paramecium is a unicellular organism that possesses a specialized pathway for regulated secretion that is amenable to genetic studies. Numerous mutations affecting the process have been isolated over the years, among which is a subclass blocking the terminal step of fusion of the secretory granule with the plasma membrane. We report herein the cloning by functional complementation of one such gene, ND7. The 506-amino acid polypeptide encoded by ND7 is predicted to be a type I integral membrane protein with a highly charged cytosolic domain featuring amphipathic and coiled-coil regions. This structure is compatible with the physiological data on the mutant nd7-1 suggesting that the protein is anchored in the membrane of the secretory granule and that it may interact with other proteins. This work presents the first identification by a genetic approach of a novel gene involved in regulated secretion and establishes Paramecium as a powerful model system for the genetic dissection of this process.
Skouri
F
F
Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
Cohen
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003593:Cytoplasm / Q000648:ultrastructure; D005089:Exocytosis; D017125:Genes, Protozoan; D005816:Genetic Complementation Test; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology*; D008969:Molecular Sequence Data; D016805:Paramecium tetraurelia / Q000235:genetics*; D015800:Protozoan Proteins / Q000502:physiology*; D015183:Restriction Mapping
D008565:Membrane Proteins; C107339:ND7 protein, Protozoa; D015800:Protozoan Proteins