Moth chemosensory protein exhibits drastic conformational changes and cooperativity on ligand binding.
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.
Campanacci
Valerie
V
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.
Lartigue
Audrey
A
Hällberg
B Martin
BM
Jones
T Alwyn
TA
Giudici-Orticoni
Marie-Thèrese
MT
Tegoni
Mariella
M
Cambillau
Christian
C
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
C435672:CSPMbraA6 protein, Mamestra brassicae; D019476:Insect Proteins; D008024:Ligands; D014364:Tryptophan