Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Information on the Waste-Disposal Units of Living Cells

12.01.2012
Berkeley Researchers Provide Detailed Look at Proteasome’s Regulatory Particle

Important new information on one of the most critical protein machines in living cells has been reported by a team of researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

The researchers have provided the most detailed look ever at the “regulatory particle” used by the protein machines known as proteasomes to identify and degrade proteins that have been marked for destruction. The activities controlled by this regulatory particle are critical to the quality control of cellular proteins, as well as a broad range of vital biochemical processes, including transcription, DNA repair and the immune defense system.

“Using electron microscopy and a revolutionary new system for protein expression, we have determined at a subnanometer scale the complete architecture, including the relative positions of all its protein components, of the proteasome regulatory particle,” says biophysicist Eva Nogales, the research team’s co-principal investigator. “This provides a structural basis for the ability of the proteasome to recognize and degrade unwanted proteins and thereby regulate the amount of any one type of protein that is present in the cell.”

Says the team’s other co-principal investigator and corresponding author, biochemist Andreas Martin, “While the biochemical function of many of the proteasome components have been determined, and some subnanometer structures have been identified, it was unclear before now which component goes where and which components interact with one another. Now we have a much better understanding as to how the proteasome machinery works to control cellular processes and this opens the possibility of manipulating proteasome activity for the treatment of cancer and other diseases.”

Nogales, who holds appointments with Berkeley Lab, UC Berkeley, and the Howard Hughes Medical Institute, and Martin, who holds appointments with UC Berkeley and the QB3 Institute, are the senior authors of a paper describing this work in the journal Nature. The paper is titled “Complete subunit architecture of the proteasome regulatory particle.” Other co-authors were Gabriel Lander, Eric Estrin, Mary Matyskiela and Charlene Bashore.

At any given moment, a human cell typically contains about 100,000 different proteins, with certain proteins being manufactured and others being discarded as needed for the cell’s continued prosperity. Unwanted proteins are tagged with a “kiss-of-death” label in the form of a polypeptide called “ubiquitin.” A protein marked with ubiquitin is delivered to any one of the some 30,000 proteasomes in the cell – barrel-shaped complexes which act as waste disposal units that rapidly break-down or degrade the protein. The 2004 Nobel Prize in chemistry was awarded to a trio of scientists who first described the proteasome process, but a lack of structural information has limited the scientific understanding of the mechanics behind this process.

Nogales, an expert on electron microscopy and image analysis, and Martin, who developed the new protein expression system used in this work, combined the expertise of their respective research groups to study the proteasome regulatory particle in yeast. The particle features 19 sub-units that are organized into two sub-complexes, a “lid” and a “base.” The lid contains the regulatory elements that identify the ubiquitin tag marking a protein for destruction, and the base features a hexameric ring that pulls the tagged protein inside the chamber of the proteasome barrel where it is degraded.

“The lid consists of nine non-ATPase proteins including ubiquitin receptors that accept properly tagged proteins but prevent a protein not marked for degradation from engaging with the proteasome,” Nogales says. “Since degradation is irreversible, it is critical that only ubiquitin-tagged proteins engage the proteasome. Interestingly, the ubiquitin tag has to be removed before the protein can be translocated into the proteasome’s destruction chamber, so the lid also contains de-ubiquitination enzymes that remove the tags after the protein has engaged with the proteasome.”

The proteasome regulatory particle’s base contains six distinct AAA+ ATPases that form the hetero-hexameric ring, which serves as the molecular motor of the proteasome.

“We predict that the ATPases use the energy of ATP binding and hydrolysis to exert a pulling force on engaged proteins, unfolding and translocating them through a narrow central pore and into the degradation chamber,” Martin says. “The steps in the proteasome process – from protein recognition to de-ubiquitination and degradation have to be very highly coordinated in time and space. Locating all of these components and identifying their relative orientations has been very telling about how the processes are coordinated with each other.”

Nogales credits the protein expression system developed by Martin and his research group, in which proteins are expressed and assembled in bacteria, as being critical to the success of this research.

“Until now researchers had to work with purified protein complexes from the cell, which could not be manipulated or modified in any way,” she says. “Andy Martin’s new heterologous expression system allows for the manipulation and dissection of protein functions. For our studies it was crucial to generate lid sub-complexes that had one marker at a time in each of the subunits so that we could determine the position of each protein within the lid. With this new system we generated truncations, deletions and fusion constructs that were used to localize individual subunits and delineate their boundaries within the lid.”

This research was supported by funds from UC Berkeley, Berkeley Lab, the National Institutes of Health, the Searle Scholars Program, the Damon Runyon Cancer Research Foundation, the American Cancer Society, the National Science Foundation and the Howard Hughes Medical Institute.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

Additional Information

For more information about Eva Nogales and her research group see http://cryoem.berkeley.edu/

For more information about Andreas Martin and his research group see http://mcb.berkeley.edu/labs/martin/amartin/Home.html

Lynn Yarris | EurekAlert!
Further information:
http://www.lbl.gov

More articles from Life Sciences:

nachricht Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society

nachricht 127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>