Pheromone binding pocket

Figure 15.7 Binding cavity of BmPBP. In the crystal structure of the BmPBP-bombykol complex (B-form) the pheromone. In the unligated acidic form of the protein (A-form), C-terminal a-helix occupies the binding pocket. This figure was prepared by Fred Damberger by using the program molmol (Koradi et al., 1996).

It is unclear how pheromone enters or exits the binding cavity. In particular, exiting the cavity is difficult, because the pheromone is completely encased in the binding pocket in most OBPs studied. It has been suggested that the low pH near a... 

In previous papers, it has been hypothesized that MUPs could act as pheromone binding proteins, since their structure, with an inner hydrophobic pocket, permits the binding and transport of putative pheromonal molecules (Bacchini et al., 1992 Bocskei et al., 1992). We were interested in testing directly the hypothesis that MUPs purified from adult male urine bind a subset of the volatile molecules found in urine and that these then act as pheromones by modifying the behaviour of mice (Mucignat-Caretta, Caretta Baldini, 1998). 

In this chapter, you will be asked to design a synthesis for bombykol, the sex pheromone of the silk moth (bombyx mori) see page 191. Molecules of bombykol diffuse through open pores in the male moth s antenna. When bombykol binds to its receptor, an electrical charge is produced that causes a nerve impulse to be sent to the brain. Bombykol, however, is a nonpolar molecule (page 555) and has to cross an aqueous solution to get to its receptor. This problem is solved by the pheromone binding protein. The protein binds bombykol in a hydrophobic pocket and then carries it to the receptor. The area around the receptor is relatively acidic, and the decrease in pH causes the pheromone binding protein to unfold and release bombykol to the receptor. 

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