Chemical Sensing: Linking sequence, mechanisms and inhibition

Oklahoma State University, Stillwater OK

Investigators

Abstract

Smita Mohanty of Oklahoma State University and Eric Anslyn of the University of Texas, Austin, are supported by an award from the Chemistry of Life Processes Program in the Division of Chemistry to investigate the biochemical and physiological mechanisms of molecular signaling in two lepidopteran insect species (moths). They seek to understand the molecular detail of how an odor is detected and communicated from the female moth to the male moth within a species during the mating process. The ability to respond to chemical stimuli such as odors is a fundamental behavior of all organisms. This project is utilizing structural and biochemical experiments to discover the basic mechanism of odor communication in two moth species, one of which is a voracious pest of crops and stored foods. Computationally-designed molecules are being synthesized and tested in the laboratory for their ability to competitively bind to odor-binding protein molecules to inhibit the sensing of female-secreted scent by the male, and thus disrupt the mating process. Knowledge gained from this research is helping bridge the fundamental gap in knowledge of the chemical and mechanistic details of sense of smell in animals, as well as paving the way for the development of novel, species-specific, and environmentally-friendly odor mimetics as alternatives to harmful pesticides, for insect control. Students at the undergraduate and graduate levels are being trained in state-of-the-art instrumentation, thus preparing the future generation of teachers, researchers, and innovators. Insects use insoluble fatty acid (FA) derivatives as highly-specific signaling molecules. Lepidopteran insects serve as a model for studying the biochemical and physiological mechanisms of FA signaling. Odor/pheromone binding proteins (OBP/PBP) ferry the fatty acid odor to the odorant receptor across the aqueous sensillar lymph that surrounds the dendrites of odor-sensitive olfactory neurons. The details of the mechanism of lipid transfer to the olfactory receptor neuron by OBPs/PBPs remain largely unknown. This project is using the combined tools and techniques of biochemistry, biophysics, molecular biology, chemical modeling, and synthetic organic chemistry to identify the chemical signatures in the protein sequences that dictate the mechanism of lipid binding and release by PBPs in two lepidopteran species: Anthereae polyphemus and Ostrinia furnacalis. The current model for lepidopteran PBPs, including Anthereae polyphemus PBP (ApolPBP1), posits a pH-dependent conformational switch for the uptake and release of the FA signal at the sensory neuron membrane. However, preliminary data for Ostrinia furnacalis PBP (OfurPBP2) suggests that this protein binds lipid and releases it through a distinct, novel mechanism. A strategy of successive mutations in ApolPBP1 residues is being used to systematically transform ApolPBP1 into an OfurPBP2 mimic, and characterize the mutants at each step using a multidisciplinary approach, to gain insight into the unique structure-function relationship and mechanism of lipid binding and release in Ostrinia furnacalis. Nature-inspired design of fatty-acid mimetics is being performed through structure-based organic synthesis, to develop a competitive inhibitor of ApoIPBP1 as a model system, and establish a design strategy for odor inhibition in the Ostrinia furnicalis pest. This combined, complementary data on two key PBP proteins is deepening the understanding of distinct mechanisms of chemical sensing, and providing a foundation for the rational design of eco-friendly biomimetic inhibitors for insect control. Educational and outreach efforts are leveraging the successful NSF REU program at Oklahoma State to recruit and train undergraduates techniques, with students actively recruited from HBCUs (Historically Black Colleges and Universities) and PUIs (Primarily Undergraduate Institutions). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.