| Title: | Amino acid residues contributing to function of the heteromeric insect olfactory receptor complex |
| Author(s): | Nakagawa T; Pellegrino M; Sato K; Vosshall LB; Touhara K; |
| Address: | "Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan" |
| DOI: | 10.1371/journal.pone.0032372 |
| ISSN/ISBN: | 1932-6203 (Electronic) 1932-6203 (Linking) |
| Abstract: | "Olfactory receptors (Ors) convert chemical signals--the binding of odors and pheromones--to electrical signals through the depolarization of olfactory sensory neurons. Vertebrates Ors are G-protein-coupled receptors, stimulated by odors to produce intracellular second messengers that gate ion channels. Insect Ors are a heteromultimeric complex of unknown stoichiometry of two seven transmembrane domain proteins with no sequence similarity to and the opposite membrane topology of G-protein-coupled receptors. The functional insect Or comprises an odor- or pheromone-specific Or subunit and the Orco co-receptor, which is highly conserved in all insect species. The insect Or-Orco complex has been proposed to function as a novel type of ligand-gated nonselective cation channel possibly modulated by G-proteins. However, the Or-Orco proteins lack homology to any known family of ion channel and lack known functional domains. Therefore, the mechanisms by which odors activate the Or-Orco complex and how ions permeate this complex remain unknown. To begin to address the relationship between Or-Orco structure and function, we performed site-directed mutagenesis of all 83 conserved Glu, Asp, or Tyr residues in the silkmoth BmOr-1-Orco pheromone receptor complex and measured functional properties of mutant channels expressed in Xenopus oocytes. 13 of 83 mutations in BmOr-1 and BmOrco altered the reversal potential and rectification index of the BmOr-1-Orco complex. Three of the 13 amino acids (D299 and E356 in BmOr-1 and Y464 in BmOrco) altered both current-voltage relationships and K(+) selectivity. We introduced the homologous Orco Y464 residue into Drosophila Orco in vivo, and observed variable effects on spontaneous and evoked action potentials in olfactory neurons that depended on the particular Or-Orco complex examined. Our results provide evidence that a subset of conserved Glu, Asp and Tyr residues in both subunits are essential for channel activity of the heteromeric insect Or-Orco complex" |
| Keywords: | "Animals Bombyx Conserved Sequence Drosophila melanogaster Insect Proteins/*chemistry/genetics/*metabolism Mesylates/metabolism Molecular Sequence Data Mutagenesis, Site-Directed Mutation *Protein Multimerization Protein Structure, Quaternary Receptors, Od;" |
| Notes: | "MedlineNakagawa, Tatsuro Pellegrino, Maurizio Sato, Koji Vosshall, Leslie B Touhara, Kazushige eng R01 DC008600/DC/NIDCD NIH HHS/ Research Support, Non-U.S. Gov't 2012/03/10 PLoS One. 2012; 7(3):e32372. doi: 10.1371/journal.pone.0032372. Epub 2012 Mar 5" |
