Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Metal ions may play big role in how we sense smells

27.02.2003


Of the five basic senses, the sense of smell is the least understood. Now, scientists at the University of Illinois at Urbana-Champaign have sniffed out potential clues to how olfactory receptors in the nose detect odors. Those clues may also explain why dietary zinc deficiencies lead to a loss of smell.

Olfactory receptors are proteins that bridge through the cell membrane. Professor Kenneth S. Suslick and co-workers have found that the structure of the protein changes dramatically when a zinc or copper ion binds to it. They propose that the olfactory response to an odorant involves this change in structure that pushes and pulls part of the olfactory receptor protein into and out of the cell in a "shuttlecock" motion. This back-and-forth motion passes information through the cell membrane. The researchers will report their findings in the Proceedings of the National Academy of Sciences. A paper on the subject is to appear in the PNAS Online Early Edition the week of Feb. 24.

The average human nose can detect nearly 10,000 distinct scents, a feat that requires about 1,000 olfactory genes, or roughly 3 percent of the human genome.



"It seems surprising that such a large percentage of our genome is dedicated to the olfactory system," said Suslick, a William H. and Janet Lycan Professor of Chemistry at Illinois. "Being visually oriented and olfactorily impaired, we tend to overlook our sense of smell. But other mammals, like dogs and rats, live or die by their sense of smell."

Knowing that molecules that bind strongly to metal ions usually smell strongly (and often badly), Suslick and his colleagues -- chemistry professor Zaida A. Luthey-Schulten and doctoral student Jiangyun Wang -- investigated the possibility that olfactory receptors are metalloproteins (proteins that contain a metal ion as part of their structure).

Inorganic chemists have long suspected that the olfactory system involved metal ions. Only recently, however, have the genes responsible for smell been identified. "When we searched the genome data, we found an identical site in more than 75 percent of the olfactory receptors that looks like it can bind to metal ions very strongly," Suslick said.

The structure of these receptors is thought to be a protein that weaves in and out of the cell membrane seven times. Between the fourth and fifth helices, the scientists found an uncommonly long loop that they suspected contained the binding site for a metal ion.

To test their theory, the researchers created synthetic peptide analogs of the potential binding site in the receptor protein. As predicted, metal ions -- particularly zinc and copper -- were bound very strongly.

The researchers then used computer models to study the behavior of olfactory receptors upon odorant binding. "Computer simulations initially put this big loop outside the cell membrane because the loop is negatively charged," Suslick said. "When a positively charged metal ion binds to the site, however, the loopÕs charge is neutralized, so the computer places the loop in the membrane."

When the long loop containing the metal ion slides into the cell membrane, a portion of the receptor protein’s fourth helix is pushed outside the membrane, Suslick said. When an odorant binds to the metal ion, the loop is ejected from the membrane, and the fourth helix is dragged back in, triggering a sequence of events leading to nerve cell activity. Then, when the odorant leaves the metal ion, the process can start over.

This back and forth movement of the protein, which the researchers refer to as a shuttlecock motion, may be a new mechanism for passing information through cell membranes.

"Another piece to this puzzle is that one of the first symptoms of dietary zinc deficiency is loss of the sense of smell," Suslick said. "That, too, is keeping with this idea that the olfactory receptors are metalloproteins."

James E. Kloeppel | UIUC
Further information:
http://www.uiuc.edu/
http://www.news.uiuc.edu/scitips/03/0221olfactory.html

More articles from Life Sciences:

nachricht Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory

nachricht Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>