Cloning and expression of a queen pheromone-binding protein in the honeybee: an olfactory-specific, developmentally regulated protein.

Odorant-binding proteins (OBPs) are small abundant extracellular proteins thought to participate in perireceptor events of odor-pheromone detection by carrying, deactivating, and/or selecting odor stimuli. The honeybee queen pheromone is known to play a crucial role in colony organization, in addition to drone sex attraction. We identified, for the first time in a social insect, a binding protein called antennal-specific protein 1 (ASP1), which binds at least one of the major queen pheromone components. ASP1 was characterized by cDNA cloning, expression in Pichia pastoris, and pheromone binding. In situ hybridization showed that it is specifically expressed in the auxiliary cell layer of the antennal olfactory sensilla. The ASP1 sequence revealed it as a divergent member of the insect OBP family. The recombinant protein presented the exact characteristics of the native protein, as shown by mass spectrometry, and N-terminal sequencing and exclusion-diffusion chromatography showed that recombinant ASP1 is dimeric. ASP1 interacts with queen pheromone major components, opposite to another putative honeybee OBP, called ASP2. ASP1 biosynthetic accumulation, followed by nondenaturing electrophoresis during development, starts at day 1 before emergence, in concomitance with the functional maturation of olfactory neurons. The isobar ASP1b isoform appears simultaneously to ASP1a in workers, but only at approximately 2 weeks after emergence in drones. Comparison of in vivo and heterologous expressions suggests that the difference between ASP1 isoforms might be because of dimerization, which might play a physiological role in relation with mate attraction.

Amino acid analysis of proteins separated by two-dimensional electrophoresis in maize: isoform detection and function identification.

The possibility of using experimentally determined amino acid composition to assess relatedness between 75 proteins separated by two-dimensional electrophoresis (2-DE) and to identify them was tested on maize. Two independent parameters, the relative Euclidean distance and the correlation coefficient between the amino acid compositions, were evaluated and used. Previous sequence information for 31 out of the 75 proteins made it possible to evaluate the method for the detection of isoforms and for identification. However, the extension of the interrogation beyond maize to all plant sequences raised the problem of false positives that could nevertheless be limited by replications and by using additional information. The efficiency of the method to assess relatedness between proteins should make amino acid composition analysis a valuable tool in large protein characterization programs based on 2-DE, by facilitating the transfer of information from one well-documented organ/tissue or genotype to another.