Functional chaperone cooperation between Hsp70 (DnaK) and Hsp104 (ClpB) was demonstrated in vitro . In a eubacterium Thermus thermophilus , DnaK and DnaJ exist as a stable trigonal ring complex ( T DnaK⋅J complex) and the dnaK gene cluster contains a clpB gene. When substrate proteins were heated at high temperature, none of the chaperones protected them from heat inactivation, but the T DnaK⋅J complex could suppress the aggregation of proteins in an ATP- and T GrpE-dependent manner. Subsequent incubation of these heated preparations at moderate temperature after addition of T ClpB resulted in the efficient reactivation of the proteins. Reactivation was also observed, even though the yield was low, if the substrate protein alone was heated and incubated at moderate temperature with the T DnaK⋅J complex, T GrpE, T ClpB, and ATP. Thus, all these components were necessary for the reactivation. Further, we found that T GroEL/ES could not substitute T ClpB.

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.