Project Summary The sense of smell provides animals with vital information about their environment. At the molecular level, olfactory stimuli consist of thousands of distinct small molecules that share no common chemical feature other than being volatile. To contend with this diversity, insects and mammals alike have evolved large families of olfactory receptors (ORs) that operate in a combinatorial way, whereby some receptors are broadly activated by many different odorants and others are exquisitely tuned to a specific compound. The molecular mechanisms that endow ORs with such diverse ligand-binding properties remain unknown, largely because the isolation and structural characterization of ORs has been a decades-long technological challenge. Using cryo-electron microscopy, I recently determined the first atomic-resolution structure of an insect OR bound to an odor. By determining the structures of additional insect ORs with broad and specific ligand-binding properties, the proposed research project will elucidate the molecular mechanism of odor detection and discrimination. To this end, the K99 mentored phase (Aim 1) will reveal the atomic structures of two primitive insect ORs with different ligand specificities unbound and in complex with multiple odor ligands, shedding light on the molecular determinants that underlie broad or specific odor selectivity. Next, the R00 independent phase (Aim 2) will focus on ORs from disease-carrying mosquitoes that participate in human host-seeking. These ORs exhibit small polymorphisms that drastically affect their ability to detect human odors. Elucidation of the atomic structure of these mosquito ORs bound to human volatiles will illuminate the molecular properties that enable mosquitoes to detect and prey on humans. Together, this research program will lend fundamental insight into the normal function of sensory processing of olfactory information. Additionally, as insect ORs are critically involved in human host-seeking that facilitates the spread of insect-borne diseases, this work will provide a foundation for the development of novel insect repellents that could curb diseases such as malaria, Zika, and dengue fever. The proposed development plan complements my training in structural biology and biophysics with computational modeling of receptor-ligand interactions and in vivo assays in Drosophila. At the end of the mentored phase, I will be equipped with the necessary tools to conduct comprehensive structural and functional studies of odor detection and discrimination by insect vectors of disease. To achieve these goals, I will take advantage of the extensive resources of the Rockefeller University, the mentorship of Dr. Vanessa Ruta and the appointment of an Advisory Committee that will lend expertise in key aspects of the project and career development. Additionally, with the support and resources from the MOSAIC/UE5 network I will expand my mentorship and leadership skills to successfully transiti...