| Title: | Residues in the first extracellular loop of a G protein-coupled receptor play a role in signal transduction |
| Author(s): | Akal-Strader A; Khare S; Xu D; Naider F; Becker JM; |
| Address: | "Department of Biochemistry, Cellular and Molecular Biology, M407 Walters Life Sciences Building, University of Tennessee, Knoxville, TN 37996, USA" |
| ISSN/ISBN: | 0021-9258 (Print) 0021-9258 (Linking) |
| Abstract: | "The Saccharomyces cerevisiae pheromone, alpha-factor (WHWLQLKPGQPMY), and Ste2p, its G protein-coupled receptor, were used as a model system to study ligand-receptor interaction. Cys-scanning mutagenesis on each residue of EL1, the first extracellular loop of Ste2p, was used to generate a library of 36 mutants with a single Cys residue substitution. Mutation of most residues of EL1 had only negligible effects on ligand affinity and biological activity of the mutant receptors. However, five mutants were identified that were either partially (L102C and T114C) or severely (N105C, S108C, and Y111C) compromised in signaling but retained binding affinities similar to those of wild-type receptor. Three-dimensional modeling, secondary structure predictions, and subsequent circular dichroism studies on a synthetic peptide with amino acid sequence corresponding to EL1 suggested the presence of a helix corresponding to EL1 residues 106 to 114 followed by two short beta-strands (residues 126 to 135). The distinctive periodicity of the five residues with a signal-deficient phenotype combined with biophysical studies suggested a functional involvement in receptor activation of a face on a 3(10) helix in this region of EL1. These studies indicate that EL1 plays an important role in the conformational switch that activates the Ste2p receptor to initiate the mating pheromone signal transduction pathway" |
| Keywords: | "Amino Acid Sequence Cysteine Gene Expression Regulation Mating Factor Molecular Sequence Data Peptides/metabolism Protein Conformation Receptors, Mating Factor Receptors, Peptide/*chemistry/physiology Signal Transduction/*physiology Structure-Activity Rel;" |
| Notes: | "MedlineAkal-Strader, Ayca Khare, Sanjay Xu, Dong Naider, Fred Becker, Jeffrey M eng GM 22086/GM/NIGMS NIH HHS/ GM 22087/GM/NIGMS NIH HHS/ Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S. 2002/06/12 J Biol Chem. 2002 Aug 23; 277(34):30581-90. doi: 10.1074/jbc.M204089200. Epub 2002 Jun 10" |
