Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Uptake Protein Acts as Zinc’s Doorway to the Cell

23.11.2010
Discovery of mechanism sheds light on how zinc — essential to the growth of all living organisms — enters cells

A study to be published as the “Paper of the Week” in the Journal of Biological Chemistry this December details how zinc, an element fundamental to cell growth, enters the cell via zinc-specific uptake proteins. The research, conducted at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, is the first to purify this kind of protein and study its role in zinc uptake.

Zinc is crucial to the health of all living organisms. At the cellular level, zinc is responsible for cell growth, which in turn affects the health, growth, and reproduction of an organism.

While there are six classes of known proteins that act as transporters or channels enabling zinc to cross the cell membrane, scientists have identified one metal-specific family of proteins whose purpose is to facilitate the cell’s zinc uptake. These are called ZIP proteins, a reference to their resemblance to zinc-regulated and ion-regulated transporter proteins.

The exact mechanism by which ZIP proteins facilitate zinc uptake has been a mystery. Brookhaven scientists led by biologist Dax Fu — who have characterized other zinc-specific proteins that maintain healthy levels of zinc on either side of the cell membrane* — have now taken a closer look at this process.

A long-held belief has posited that ZIP proteins work like elevators, pumping zinc across the cell membrane and into the cell. However, Fu and his colleagues found no evidence to support this explanation.

“This was a big surprise. For the last fifteen years, the assumption has been that the ZIP protein acts like a pump or elevator,” said Fu. “Instead, we have found that ZIP is more like a door.”

Fu and his colleagues have studied a ZIP protein provided by the New York Consortium on Membrane Protein Structure and derived from the bacteria Bordatella bronchiseptica. They expressed the protein in Eschericia coli, a bacteria whose zinc regulation has been well documented. Brookhaven’s Jin Chai purified and concentrated the samples before exposing them to zinc. By reconstituting the purified ZIP proteins in this controlled manner, the scientists ensured that their sample would reflect only the ZIP mechanism for cellular zinc uptake.

“It’s important to note that people have been trying to purify these proteins for a long time. Purification of the first ZIP family member opens the door for detailed structural and functional analysis at the molecular level,” Fu said.

Using a fluorescent indicator, Brookhaven’s Wei Lin then conducted several measurements to characterize zinc uptake, with attention to changes in zinc concentration, temperature, acidity, and electric charge.

The Brookhaven team found evidence of electrodiffusion. Ions diffuse by moving from a region with a high concentration to one of a lower concentration — like diners who relocate from a crowded dining hall to an adjoining, empty coffee room. In electrodiffusion, the diffused ions also change the electric charge of the space that they occupy. The imbalance in charge created by zinc ions moving into the cell builds during zinc uptake and acts against the concentration gradient, eventually causing zinc uptake to stop.

Based in part on the studies of similar metal-specific proteins, Fu and his colleagues have postulated that the ZIP protein allows zinc ion diffusion by providing an opening that is specifically shaped for zinc coordination chemistry. This hypothesis will eventually be confirmed in studies that crystallize and examine the ZIP protein at the atomic level.

“We are driven by our curiosity — we want to know how this works,” Fu said.

Aside from satisfying scientific curiosity, this understanding could have a big impact. Zinc uptake at the cellular level is implicated in a range of biomedical and energy research. For example, in green plants, carbonic acid is converted to CO2 in a chemical reaction that is catalyzed by a zinc enzyme.

Zinc deficiency, therefore, has a direct impact on the carbohydrate metabolism of plants. For researchers developing biofuels energy sources, these systems and the role of zinc transporters in the conversion of energy into carbohydrates, are important objects of study. Developing a better understanding of zinc uptake can provide greater insight into these processes and will inform future discoveries.

In addition to the Brookhaven researchers, James Love of the New York Structure Biology Center contributed to this research. Funding and support for the work came from the DOE Office of Science and from the National Institutes of Health.

Karen McNulty Walsh | EurekAlert!
Further information:
http://www.bnl.gov

More articles from Life Sciences:

nachricht Study shines light on brain cells that coordinate movement
26.06.2017 | University of Washington Health Sciences/UW Medicine

nachricht New insight into a central biological dogma on ion transport
26.06.2017 | Aarhus University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>