Now, University of Otago zoology neurobiology researcher Dr Bart Geurten has helped solve the scientific mystery.
He said the key lay in mechanosensory transduction channels — proteins in our cells that converted physical forces into electrical signals.
They are the sensors for a number of systems including the senses of touch, hearing and balance, as well as participating in cardiovascular regulation and osmotic homeostasis (thirst).
"But these channels need a built-in flexibility.
"If they’re too rigid, they’d stay stuck open or closed. Too loose, and they’d be unreliable.
"In our study, we discovered that mechanosensory channels work the same way.
"The hinge, located between the force-sensing and gate regions of the NOMPC [no mechanoreceptor potential C] ion channel in fruit flies, provides the elasticity needed to fine-tune sensitivity."
He said the idea was first proposed in 1983, but until now, no-one had been able to pinpoint what this "spring" actually was, or where it was situated.
"In our new study, published in Nature Neuroscience, we finally found it — a hinge-like structure within the NOMPC ion channel in fruit fly ears.
"This hinge sits between the part of the protein that senses force and the channel’s gate, working much like the swinging saloon doors in a Wild West movie.
"Without the hinge, the doors [or channels] would either stay open or closed permanently, making them useless for sensing fine details."
Dr Geurten said the hinge was not unique to fruit flies.
When the researchers compared it across species, they found similar structures in bacteria, other flies, and even humans.
"This suggests it could be a fundamental mechanism in sensory evolution, affecting how we experience everything from hearing to balance."
While it was too soon to say how the discovery would impact medical research, he said understanding how sensory proteins worked at this level could eventually have implications for conditions like age-related hearing loss.
"For now though, it’s just incredibly exciting to finally put a face to the ‘gating spring’ that scientists have been searching for since the
1980s."
