NMR Studies of Insect Pheromone-binding Proteins

Odorant-binding proteins (OBPs) occur at high concentrations in the lymph of insect olfactory sensilla and transport the hydrophobic odorant molecules from the periphery of the sensillum to the olfactory receptors. The pheromone-binding proteins (PBPs) are a subclass of the OBPs which bind pheromones used in insect communication. Our work so far shows that the pheromone-binding protein from the silkmoth Bombyx mori (BmPBP) undergoes a pH-dependent conformational transition between two forms (BmPBPA observed at pH 4.5 and BmPBPB at pH 6.5), which is likely to relate to biological function. To obtain a more complete picture of the function of BmPBP, we have determined the solution structures at pH 4.5 and pH 6.5. Strikingly, the C-terminal dodecapeptide segment, which is disordered on the protein surface in BmPBPB and in the crystal structure of the BmPBP-bombykol complex, forms a regular alpha-helix in BmPBPA, which is inserted into the core of the protein and occupies the ligand binding site. This explains the absence of binding observed for BmPBP at pH 4.5. BmPBP represents a novel mechanism of intramolecular protein regulation involving regions distant in the sequence. We are following up on these initial results with further studies of BmPBP, designed variants of this protein under variable solution conditions, and PBPs from different insect species to provide further insight into the structure-function correlations.

Keywords

Bombyx mori, Pheromone-binding Proteins, NMR structure determination

Contacts

Dr. Fred Damberger, Prof. Kurt Wüthrich

Electronic Contacts

fred.damberger@mol.biol.ethz.ch
kurt.wuthrich@mol.biol.ethz.ch

In Collaboration With:

Prof. Walter S. Leal, University of California, Davis, CA 95616, USA

Support

ETH Zürich