The encapsulin nanocompartment from Rhodococcus erythropolis N771 (Reencapsulin) was expressed and purified in wild-type and C-terminally His-tagged forms. Negative-stained transmission electron microscopy, fieldflow fractionation combined with multi-angle light scattering and dynamic light scattering analyses showed that 60 Reencapsulin monomers were assembled as a spherical particle with a diameter of 28 nm. Heterogeneous guest proteins such as EGFP and firefly luciferase were packaged into the internal cavity of the Reencapsulin nanocompartment by fusing the C-terminal 37-amino-acid sequence of the R. erythropolis N771 DypB peroxidase to the C-terminus. Reencapsulin has the potential to package target proteins in its internal cavity and/or display them on its external surface, making it a feasible carrier for nanotechnology applications.

Olfactory systems have evolved the extraordinary capability to detect and discriminate volatile odorous molecules (odorants) in the environment. Fundamentally, this process relies on the interaction of odorants and their cognate olfactory receptors (ORs) encoded in the genome. Here, we conducted a cell-based screen using over 800 mouse ORs against seven odorants, resulting in the identification of a set of high-affinity and/or broadly-tuned ORs. We then test whether heterologously expressed ORs respond to odors presented in vapor phase by individually expressing 31 ORs to measure cAMP responses against vapor phase odor stimulation. Comparison of response profiles demonstrates this platform is capable of discriminating between structural analogs. Lastly, co-expression of carboxyl esterase Ces1d expressed in olfactory mucosa resulted in marked changes in activation of specific odorant-OR combinations. Altogether, these results establish a cell-based volatile odor detection and discrimination platform and form the basis for an OR-based volatile odor sensor.