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 Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

nachricht The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>