Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Test for Dioxin Sensitivity in Wildlife Could Result from New Study

22.05.2006


Why are chickens so sensitive to dioxins, but terns seem much more resistant, despite their exposure through eating dioxin-tainted fish? The life-or-death difference researchers have found can be partially explained by two amino acids in the chain of 858 amino acids that form one critical protein.



The slight difference apparently changes the three-dimensional shape of the protein, known as the aryl hydrocarbon receptor, allowing dioxin to bind more easily to the chicken receptor’s dioxin-binding site, like a key in a lock, and trigger harmful effects. The dioxin “key” does not fit as smoothly into the tern receptor’s binding site.

The findings, reported recently in the Proceedings of the National Academy of Sciences, advance the possibility of a test that wildlife managers could use to assess dioxin sensitivity in wild animal populations, said Sibel Karchner, a researcher at Woods Hole Oceanographic Institution (WHOI) and lead author of the PNAS paper.


Dioxins are a group of chemical compounds with similar chemical structures and biological characteristics. Present in the environment worldwide, they are formed as an unintentional by-product of many industrial processes involving chlorine such as waste incineration, chemical and pesticide manufacturing, the production of PVC plastics and paper, and from forest fires and backyard burning. Dioxins and structurally related chemicals can cause an array of disorders in most vertebrate animals and have been linked to cancer and reproductive abnormalities in humans. Dioxin was the primary toxic component of the defoliant Agent Orange, and was found at Love Canal in Niagara Falls, NY.

In virtually all vertebrates, dioxin sticks or binds to the aryl hydrocarbon receptor, or AHR. Like any protein, AHR is coded for by a gene, whose DNA sequence dictates the exact sequence of amino acid “building blocks” joined together to make the protein. The particular sequence of amino acids determines how the protein folds into a specific three-dimensional shape.

Somewhere in that folded shape is a region where the dioxin molecule fits—the binding site. Once bound, the AHR-dioxin combination alters the function of other genes in the cell, triggering harmful effects. Without that “lock” region, the dioxin “key” cannot bind and trigger those harmful effects. Laboratory mice engineered to lack AHR are not affected by dioxin, while mice with AHR are poisoned by it.

Chicken and tern AHR proteins are 858 and 859 amino acids long, respectively. Karchner and colleagues used molecular cloning techniques to determine the entire sequence of amino acids for each receptor protein. They showed that the chicken AHR has a 7-fold higher affinity for dioxin than the tern AHR, providing a molecular explanation for at least part of the difference in sensitivity between these species. They then traced the difference in affinity to the dioxin-binding regions of the chicken and tern proteins. Additional experiments showed that only two of the 168 amino acids in this region were responsible for the difference.

“These two amino acids account for the entire difference in binding affinity for dioxin, and therefore have a major impact on the difference in sensitivity between chicken and tern,” Karchner said.

The AHR protein has been well studied in mammals, but has not been as extensively characterized in non-mammalian vertebrates. The protein has a similar structure in different animals, which suggests that it originated long ago in evolutionary time. “It is a very old protein, and many of the amino acid sequences in this region of the protein have been kept similar over time⎯what is known as highly conserved sequences,” said Karchner. This high similarity allows the researchers to compare the AHR among different species. Cloning, in vitro expression, and analysis of protein function provide a promising method to study the potential impact of environmental contaminants on protected species.

“We looked at only two birds, the domestic chicken (Gallus gallus) and the common tern (Sterna hirundo),” Karchner said, “but you might be able to predict sensitivity of other wild animals by looking at a short section of a gene or protein sequence rather than conducting extensive studies on entire, large genes.” The authors report that other "less-sensitive" bird species share the same two critical amino acids as the common tern.

The research team included Karchner, Diana G. Franks and Mark E. Hahn of WHOI and Sean W. Kennedy from Environment Canada, National Wildlife Research Centre. In collaboration with Hahn and Karchner, Kennedy is continuing to collect samples from many species of wild birds to compare their AHRs. Hahn and others are pursuing similar studies in several species of marine mammals.

The study was supported with funding from the Woods Hole Sea Grant program.

Shelley Dawicki | EurekAlert!
Further information:
http://www.whoi.edu

More articles from Studies and Analyses:

nachricht Antarctic Ice Sheet mass loss has increased
14.06.2018 | Technische Universität Dresden

nachricht WAKE-UP provides new treatment option for stroke patients | International study led by UKE
17.05.2018 | Universitätsklinikum Hamburg-Eppendorf

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

Im Focus: Water is not the same as water

Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.

From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

A sprinkle of platinum nanoparticles onto graphene makes brain probes more sensitive

15.06.2018 | Materials Sciences

100 % Organic Farming in Bhutan – a Realistic Target?

15.06.2018 | Ecology, The Environment and Conservation

Perovskite-silicon solar cell research collaboration hits 25.2% efficiency

15.06.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>