Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Insights gained from molecular modeling may lead to better insecticides

25.02.2004


One of the most damaging crop pests, the corn earworm, may be outwitting efforts to control it by making structural changes in a single metabolic protein, but new insights uncovered by molecular modeling could pave the way for more efficient insecticides, say researchers at the University of Illinois at Urbana-Champaign.


The modeled structure of the CYP6B8 protein in the corn earworm (Helicoverpa
zea). A potential substrate binding cavity, in green, where insecticides or plant defense chemicals can be detoxified, is shown above the heme, the small complex that includes the red sphere at its center
Photo courtesy of Jerome Baudry



In a study that compared the ability of corn earworms (Helicoverpa zea) and black swallowtail butterflies (Papilio polyxenes) to neutralize insecticides and plant defense allelochemicals that target insect herbivores, researchers focused on the insectsÕ primary detoxifying cytochrome P450 enzymes.

The study was published online Monday (Feb. 23) in advance of regular publication in the Proceedings of the National Academy of Sciences.


Earworms, which can feed on hundreds of different kinds of plants, have evolved generalist counter-defense P450 proteins that can process more diverse arrays of harmful agents than can similar proteins in black swallowtails, which consume a restricted diet of only two plant families.

Predictive three-dimensional modeling of the structures of the proteins detoxifying allelochemicals and insecticides has indicated vivid differences in the catalytic sites of CYP6B1, the P450 in black swallowtails, and CYP6B8, the P450 protein in earworms.

Because the corn earwormÕs metabolic protein is more flexible, it can bind to and detoxify six different kinds of plant defense chemicals as well as three common insecticides, said Jerome Baudry, a senior research scientist in the School of Chemical Sciences at Illinois. "This generalist insect has adapted to the natural chemical defenses of plants so that it can feed on a wider variety of plants," he said.

The P450 studied in the specialist is significantly more constrained. It contains a more rigid catalytic pocket that restricts the range of plant chemicals and insecticides that can enter and be processed, Baudry said.

While the specialization allows for much higher rates of detoxification of chemicals that black swallowtails normally encounter, they can handle few other toxins. In the study, the CYP6B1 protein metabolized only two plant defense chemicals and one insecticide.

"This is the first clear demonstration that resistance to plant allelochemicals and insecticides can be acquired by changes within a single P450 catalytic site," said Mary A. Schuler, a professor of cell and structural biology. "If you can identify the P450 responsible for metabolizing insecticides and find a way to inactivate its catalytic site, you kill the P450 and prevent it from detoxifying insecticides."

Accomplishing that, however, wonÕt be easy because there is at least one other P450 in corn earworms that also handles insecticides, she said. "To truly hit the earworms, you would need to find one inhibitor that can kill both enzymes. Ultimately, it may be possible to use a synergistic approach that would kill more insects using significantly lower levels of insecticides, thereby reducing the toxicity of insecticides in the environment," she said.

Structural differences of the P450s involved in these chemical detoxifications result from changes in the arrangement of amino acids within the catalytic sites. In the black swallowtailÕs version, aromatic rings protrude into the substrate binding site, creating a rigid space in which allelochemicals or insecticides must fit exactly Ð like keys going into locks, Baudry said. The amino acid residues in the catalytic site stabilize the toxic substrate so it is optimally bonded with the proteinÕs heme, an iron-containing pigment in the catalytic site that mediates oxidation of the chemical to a non-toxic product.

In the earworm protein, many of the aromatic rings are missing, creating a much more accessible and flexible catalytic site. As a result, toxins of many different shapes and sizes can enter and be detoxified. Since the toxins are not as rigidly restricted, they are not detoxified quite as efficiently as some of the toxins encountered by the specialist P450.

"The corn earworm thus is jack of many trades but master of none, but this biochemical ability allows it to acquire new host plants and overcome new pesticides with relative ease," said co-investigator May R. Berenbaum, the head of the entomology department at Illinois and an expert on allelochemicals.


Xianchun Li, a doctoral student in entomology, also was a coauthor of the paper and a major contributor to the research.

The study was funded by grants from the U.S. Department of Agriculture to Schuler and Berenbaum, a grant from the National Institutes of Health to Schuler, and a China Natural Science Foundation grant to Li.

Jim Barlow | UIUC
Further information:
http://www.news.uiuc.edu/news/04/0224insects.html
http://www.uiuc.edu/index.html

More articles from Agricultural and Forestry Science:

nachricht Faba fix for corn's nitrogen need
11.04.2018 | American Society of Agronomy

nachricht Wheat research discovery yields genetic secrets that could shape future crops
09.04.2018 | John Innes Centre

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

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

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

Im Focus: The Future of Ultrafast Solid-State Physics

In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.

Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Diamond-like carbon is formed differently to what was believed -- machine learning enables development of new model

19.04.2018 | Materials Sciences

Electromagnetic wizardry: Wireless power transfer enhanced by backward signal

19.04.2018 | Physics and Astronomy

Ultrafast electron oscillation and dephasing monitored by attosecond light source

19.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>