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 Kakao in Monokultur verträgt Trockenheit besser als Kakao in Mischsystemen
18.09.2017 | Georg-August-Universität Göttingen

nachricht Ultrasound sensors make forage harvesters more reliable
28.08.2017 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP

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: 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 >>>