Featured Research

from universities, journals, and other organizations

Insights Gained From Molecular Modeling May Lead To Better Insecticides

Date:
February 25, 2004
Source:
University Of Illinois At Urbana-Champaign
Summary:
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.

CHAMPAIGN, Ill. -- 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.

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 Š 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.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "Insights Gained From Molecular Modeling May Lead To Better Insecticides." ScienceDaily. ScienceDaily, 25 February 2004. <www.sciencedaily.com/releases/2004/02/040225071016.htm>.
University Of Illinois At Urbana-Champaign. (2004, February 25). Insights Gained From Molecular Modeling May Lead To Better Insecticides. ScienceDaily. Retrieved August 28, 2014 from www.sciencedaily.com/releases/2004/02/040225071016.htm
University Of Illinois At Urbana-Champaign. "Insights Gained From Molecular Modeling May Lead To Better Insecticides." ScienceDaily. www.sciencedaily.com/releases/2004/02/040225071016.htm (accessed August 28, 2014).

Share This




More Plants & Animals News

Thursday, August 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Australian Sheep Gets Long Overdue Haircut

Raw: Australian Sheep Gets Long Overdue Haircut

AP (Aug. 28, 2014) — Hoping to break the record for world's wooliest, Shaun the sheep came up 10 pounds shy with his fleece weighing over 50 pounds after being shorn for the first time in years. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Minds Blown: Scientists Develop Fish That Walk On Land

Minds Blown: Scientists Develop Fish That Walk On Land

Newsy (Aug. 28, 2014) — Canadian scientists looking into the very first land animals took a fish out of water and forced it to walk. Video provided by Newsy
Powered by NewsLook.com
Super Healthful Fruits and Vegetables: Which Are Best?

Super Healthful Fruits and Vegetables: Which Are Best?

Ivanhoe (Aug. 27, 2014) — We all know that it is important to eat our fruits and vegetables but do you know which ones are the best for you? Video provided by Ivanhoe
Powered by NewsLook.com
Bad Memories Turn Good In Weird Mouse Brain Study

Bad Memories Turn Good In Weird Mouse Brain Study

Newsy (Aug. 27, 2014) — MIT researchers were able to change whether bad memories in mice made them anxious by flicking an emotional switch in the brain. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins