Featured Research

from universities, journals, and other organizations

Researchers Witness Assembly Of Molecules Critical To Protein Function

Date:
June 20, 2008
Source:
Virginia Tech
Summary:
Iron-sulfur clusters are critical to life on earth. They are necessary for protein function in cellular processes, such as respiration in humans and other organisms and photosynthesis by plants. A research group has isolated proteins responsible for the iron-sulfur cluster assembly process and witnessed the necessary protein interactions in vivo -- within a cell.

Depicted is a molecular representation of a four iron- four sulfur cluster in which the sulfur is shown in yellow and iron in green.
Credit: Callie Raulfs

A Virginia Tech research group lead by two biochemistry graduate students has isolated proteins responsible for the iron-sulfur cluster assembly process and witnessed the necessary protein interactions in vivo -- within a cell. They have captured pathway intermediates and observed protein interactions between the two major players in iron-sulfur cluster assembly.

Iron-sulfur clusters are critical to life on earth. They are necessary for protein function in cellular processes, such as respiration in humans and other organisms and photosynthesis by plants. "But we do not understand how Fe-S molecules are made or the specifics of how they bond," said Callie Raulfs of Christiansburg, Va. "It does not happen spontaneously. It has to be regulated."

Diseases such as Friedrich's ataxia and several types of anemia are a result of iron-sulfur cluster (ISC) assembly malfunctions.

Using genetic and biochemical techniques, Ph.D. students Raulfs and Ina P. O'Carroll, of Tirana, Albania, have isolated components of the ISC machinery in the process of making iron-sulfur clusters. "This work provides insight into the sequential steps of the iron-sulfur cluster assembly process, helping to explain how molecules of iron and sulfur are synthesized and distributed in cells," said O'Carroll.

Previous studies by Dean and others have demonstrated that proteins can assemble clusters from components in vitro systems -- that is, outside of an organism. Ten years ago, working with nitrogen-fixation systems, Dean's lab was the first to discover ISC proteins. Now Dean's students, Raulfs and O'Carroll, are the first to witness the assembly process in vivo -- within a cell.

"The cool thing is we've come up with a way to observe ISC proteins from their native host with a cluster attached," said O'Carroll. "The system also allows us to capture different phases of the process."

The students have isolated three different intermediates of the ISC proteins involved in intercellular biosynthesis -- or the cluster assembly process.

Rather than multiplying the proteins by placing them in E. coli, the Virginia Tech team used Azotobacter vinelandii, an aerobic, soil microbe that fixes nitrogen from the atmosphere, to obtain natural levels of the ISC proteins. "A vinelandii grows quickly and keeps the interior of the cell free of oxygen, which is important, since oxygen can destroy Fe-S clusters," said Raulfs, who first isolated a protein complex with a cluster attached, providing in vivo evidence that the two proteins get together and form a cluster.

"Because we are isolating proteins from the cell, we are also able to observe interactions between different Fe-S cluster asembly proteins," said O'Carroll. "We have been able to isolate a complex between the two major players in iron-sulfur assembly, the cluster assembly scaffold (IscU) and the sulfur-delivery protein (IscS)."

The methodology is to add a histidine amino acid tag to the ISC proteins "so we can fish the proteins out of the cell," said O'Carroll.

"Because we are fishing the cluster-containing protein out of the cell that has all of the other assembly proteins present at physiological levels, we are able to observe what else comes with the protein. What was really exciting in this case was that we saw large amounts of one of the other iron sulfur cluster assembly protein, IscS." said O'Carroll.

The work marks the first time researchers have been able to observe ISC proteins from the balanced environment of the native cell.

Next, they plan to determine the role of the individual genes in the set that produces ISC proteins in order to determine the effect of each gene on the assembly process. "The goal is to determine the events and the order in the ISC assembly process so we can figure out how cells make clusters and deliver them to specific target proteins," said O'Carroll.

The researchers are now developing a system that others can use to study proteins.

Raulfs received her undergraduate degree from the College of William and Mary. She has been a fellow in the Exploring Interfaces through Graduate Education and Research (EIGER) project, a National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) program at Virginia Tech.

O'Carroll received her undergraduate degree from McDaniel College. Dos Santos is the senior postdoc in the Dean lab. Unciuleac is now a post-doctoral fellow with the Molecular Biology Program at the Sloan-Kettering Institute.

The research is supported by the National Science Foundation.


Story Source:

The above story is based on materials provided by Virginia Tech. Note: Materials may be edited for content and length.


Journal Reference:

  1. Raulfs, O'Carroll, Patricia C. Dos Santos, Mihaela-Carmen Unciuleac, Dennis R. Dean. In vivo iron-sulfur cluster formation. Proceedings of the National Academy of Science, Online week of June 16-20, 2008

Cite This Page:

Virginia Tech. "Researchers Witness Assembly Of Molecules Critical To Protein Function." ScienceDaily. ScienceDaily, 20 June 2008. <www.sciencedaily.com/releases/2008/06/080616170813.htm>.
Virginia Tech. (2008, June 20). Researchers Witness Assembly Of Molecules Critical To Protein Function. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2008/06/080616170813.htm
Virginia Tech. "Researchers Witness Assembly Of Molecules Critical To Protein Function." ScienceDaily. www.sciencedaily.com/releases/2008/06/080616170813.htm (accessed July 30, 2014).

Share This




More Plants & Animals News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Raw: Otters Enjoy Water Slides at Japan Zoo

Raw: Otters Enjoy Water Slides at Japan Zoo

AP (July 30, 2014) River otters were hitting the water slides to beat the summer heatwave on Wednesday at Ichikawa City's Zoological and Botanical Garden. (July 30) Video provided by AP
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