Structure and Function of Odorant Binding Proteins and Chemosensory Proteins in Moths

Sammanfattning: Odorant Binding Proteins (OBPs) and Chemosensory Proteins (CSPs) are small soluble proteins found in the lymph of insect sensillae located on insect antennae. Odorant Binding proteins are implied in olfaction, by binding hydrophobic odorant molecules and transporting them to the olfactory receptor located on the dendrite of the olfactory neurons. They are divided into three groups, Pheromone Binding Proteins (PBPs), General Odorant Binding Proteins (GOBPs) and Antennal Binding Proteins X (ABPs), and each of them may heve different binding abilities. PBPs and GOBPs are specific of Lepidoptera. Chemosensory Proteins may have the same function of solubilisation and transport of chemosensory molecules. In this thesis, the respective roles of GOBPs and CSPs was investigated using molecular tools. GOBPs from two classes, GOBP1 and GOBP2 were cloned fom two noctuid species, Agrotis ipsilon and Agrotis segetum and their expression within the body and during the development was studied, showing that GOBP2 and GOBP1 are both expressed in male and female antennae, and that GOBP2 is in addition expressed in male legs. Furthermore, GOBP2 is expressed from fifth instar larva to the begining of the pupal stage, whereas GOBP1 expression is restricted to the adult, suggesting a different role for these two classes of proteins that yet remains to be determined. By analysing genome of Bombyx mori, thirteen CSP genes have been discovered. Each of these genes product has a different localization in the insect body, and some of them are expressed in organs not dedicated to chemosensation, suggesting a broader role than chemosensation for these proteins. The B. mori CSP1 protein (BmorCSP1) is mainly expressed in antennae and legs, and could be implied in chemosensation. We therefore determined the three-dimensional structure of the Bombyx mori CSP1 (BmorCSP1) to possibly better understand the function of this protein. BmorCSP1 is an a-helical protein. It has the shape of a prism and an internal cavity that could bind B. mori mori pheromones or given its lmocalisation in antennae and legs, odorant molecules. All data so far obtained for GOBP and CSPs suggest a different role for these two proteins taht yet remains to be determined.