Complete NMR chemical shift assignments of odorant binding protein 22 from the yellow fever mosquito, Aedes aegypti, bound to arachidonic acid

Abstract

Aedes aegypti mosquitoes are the vector for transmission of Dengue, Zika and chikungunya viruses. These mosquitos feed exclusively on human hosts for a blood meal. Previous studies have established that Dengue virus infection of the mosquito results in increased expression of the odorant binding proteins 22 and 10 within the mosquito salivary gland and silencing of these genes dramatically reduces blood-feeding behaviors. Odorant binding proteins are implicated in modulating the chemosensory perception of external stimuli that regulate behaviors such as host location, feeding and reproduction. However, the role that AeOBP22 plays in the salivary gland is unclear. Here, as a first step to a more complete understanding of the function of AeOBP22, we present the complete backbone and side chain chemical shift assignments of the protein in the complex it forms with arachidonic acid. These assignments reveal that the protein consists of seven α-helices, and that the arachidonic acid is bound tightly to the protein. Comparison with the chemical shift assignments of the apo-form of the protein reveals that binding of the fatty acid is accompanied by a large conformational change in the C-terminal helix, which appears disordered in the absence of lipid. This NMR data provides the basis for determining the structure of AeOBP22 and understanding the nature of the conformational changes that occur upon ligand binding. This information will provide a path to discover novel compounds that can interfere with AeOBP22 function and impact blood feeding by this mosquito.