Prions are thought to cause severe brain diseases
The brain protein which has a hand, when defective, in the lethal disease CJD may also be involved in aiding our sense of smell.
Mice bred to lack the prion protein could not find buried food or choose between smells.
Columbia University scientists said some symptoms of prion disease might be due to the loss of the protein's original role.
The study was published in the journal Nature Neuroscience.
The prion protein has historically received something of a bad press, being blamed in its misshapen form for degenerative brain diseases in humans and other animals.
However, many scientists have been trying to uncover what it actually does when it is behaving correctly.
Dr Stuart Firestein's team believe that one of these roles is to help us smell.
While his prion-protein free mice were still able to detect scents, they had lost some higher functions which required that smell information to be analysed and processed by the brain.
The scientists found changes in the communication between neurons in the nerve cells of the olfactory bulb, part of the forebrain which deals with odours.
When the protein was restored to this part of the brain, the ability to discriminate between odours came back.
The scientists said that while the discovery had no direct link to the diseases caused by faulty prion proteins, it might help account for some of the symptoms experienced by patients, which might be due to the failure of the proteins to do their normal job properly, rather than the damage caused by accumulation of defective prions.
This is not the first suggested role for the prion protein - in 2007, Leeds University scientist Professor Nigel Hooper said that it might help reduce the formation of "plaques" linked to the onset of Alzheimer's Disease.
He said of the newly-reported research : "It's likely that these proteins have a number of roles in various different body systems, including the olfactory system, as suggested here.
"I don't think you can say that it is so mysterious any more, or that we do not understand what it does."