Muscone-specific olfactory protein MjavOBP3 identified as the putative scent-marking pheromone in the Sunda pangolin (Manis javanica)

Pangolins are mammals of important conservation interest, as only eight extant species remain globally and all are considered to be at risk of extinction. The Sunda pangolin (Manis javanica) is a burrowing and nocturnal animal with poor vision, thus intraspecies communication such as mating, warning, and scent-marking relies on olfaction. The specific pheromone involved in intraspecies communication in pangolins remains unknown. In this study, all odorant-binding proteins in Sunda pangolins are functionally expressed and screened against a panel of 32 volatiles that derived from the pangolin urine, feces, and anal gland secretions. Using reverse chemical ecology, we reveal that M. javanica odorant-binding protein 3 (MjavOBP3) possesses the highest binding affinity to muscone. We also apply a behavior-tracking assay to show that muscone is more attractive to male individuals than to females, suggesting that muscone is a scent-marking pheromone in the Sunda pangolin. Further, our molecular modeling shows that Tyr117 contributes the most to muscone binding, which is further validated by site-directed mutagenesis. These findings identify the scent-marking mechanism in pangolins, highlighting the potential of muscone to support monitoring and conservation of this endangered animal.