title: Moth chemosensory protein exhibits drastic conformational changes and cooperativity on ligand binding.
abstract: Chemosensory proteins (CSPs) have been proposed to transport hydrophobic chemicals from air to olfactory or taste receptors. They have been isolated from several sensory organs of a wide range of insect species. The x-ray structure of CSPMbraA6, a 112-aa antennal protein from the moth Mamestra brassicae (Mbra), was shown to exhibit a novel type of alpha-helical fold. We have performed a structural and binding study of CSPMbraA6 to get some insights into its possible molecular function. Tryptophan fluorescence quenching demonstrates the ability of CSPMbraA6 to bind several types of semio-chemicals or surrogate ligands with microM K(d). Its crystal structure in complex with one of these compounds, 12-bromo-dodecanol, reveals extensive conformational changes on binding, resulting in the formation of a large cavity filled by three ligand molecules. Furthermore, binding cooperativity was demonstrated for some ligands, suggesting a stepwise binding. The peculiar rearrangement of CSPMbraA6 conformation and the cooperativity phenomenon might trigger the recognition of chemicals by receptors and induce subsequent signal transduction.
authors.affiliation: Architecture et Fonction des Macromolécules Biologiques, Unité Mixte de Recherche 6098, Centre National de la Recherche Scientifique and Universités d'Aix-Marseille I & II, 31 Chemin J. Aiguier, 13402 Marseille Cedex 20, France.
authors.forename: Valerie
authors.initials: V
authors.lastname: Campanacci
authors.forename: Audrey
authors.initials: A
authors.lastname: Lartigue
authors.forename: B Martin
authors.initials: BM
authors.lastname: Hällberg
authors.forename: T Alwyn
authors.initials: TA
authors.lastname: Jones
authors.forename: Marie-Thèrese
authors.initials: MT
authors.lastname: Giudici-Orticoni
authors.forename: Mariella
authors.initials: M
authors.lastname: Tegoni
authors.forename: Christian
authors.initials: C
authors.lastname: Cambillau
mesh_terms: D000818:Animals; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D009036:Moths; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000378:metabolism
chemical_list: C435672:CSPMbraA6 protein, Mamestra brassicae; D019476:Insect Proteins; D008024:Ligands; D014364:Tryptophan