Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Catching A Sneak

14.04.2005


Weizmann Institute Scientists Reveal the Shape of a Protein That Helps Retroviruses Break into Cells



Retroviruses are among the trickier and more malicious disease agents, causing AIDS and cancers such as leukemia. The viruses manage to sneak into cells with the help of special protein assemblies scattered all over their surfaces. These retrovirus surface proteins cause the membrane envelope of the virus to fuse with the membrane of the cell, spilling virus RNA into the cell to wreak damage. Now, a team of scientists at the Weizmann Institute of Science and the Max Planck Institute for Biochemistry has obtained a close-up 3-D portrait of the large protein complex on the virus that enables its entry into the cell. Their work appeared in the Proceedings of the National Academy of Sciences, USA in March.

These protein complexes recognize and bind to specific sites on the cellular membrane and mediate the fusion process, the first steps in virus infection. However, the shape of this complex on retroviruses and the way that it works had long evaded efforts at detection by various scientific groups. The difficulty is that crystallization, the leading method of preparing proteins for structure solving, does not work well with the elaborate, envelope-bound complexes, which tend to fall apart when they are removed from the virus membrane. Dr. Deborah Fass of the Weizmann Institute’s Structural Biology Department had managed to determine the structures of assorted parts of the complex in the past, but needed a better understanding of how the complex works as a whole.


To accomplish her goal, Fass and student Nathan Zauberman teamed up with scientists from Max Planck’s Molecular Structural Biology Department in Martinsried, Germany to try an alternative method of getting an image of the complex. They turned to the electron microscope, a standard tool for observing larger structures such as cell sections.

Viewing a single, relatively small protein complex was pushing the limits of this technology, but the Max Planck group, expert at developing both the hardware and the software required for visualizing biological structures using electron microscopy, was up to the task. The technique used, known as cryo-electron tomography, involved quick-freezing the viruses in liquid ethane, capturing snapshots of them at various angles and then combining the snapshots to create three-dimensional pictures. From dozens of these digitized 3-D pictures of whole viruses, hundreds of protruding surface protein complexes could be cut out, aligned, and averaged. Though the resulting image did not have quite as high a resolution as those obtained through crystallography, it allowed the scientists to get a complete and fairly detailed picture of this important protein complex in its natural environment. “After years of trying to imagine how the pieces fit together, suddenly we had the real structure right in front of us. Some aspects of it looked familiar, but others were completely unanticipated,” says Fass.

The scientists were surprised to note that the shape of the complexes on the retroviruses bore little resemblance to other known viral envelope protein structures such as those on flu viruses. They also saw strong evidence that the protein complex undergoes a radical change in shape and arrangement of its component parts as it attaches to cells and initiates membrane fusion. Fass was able to see how a smaller protein piece she had previously isolated and analyzed by crystallization fit into the whole, giving her further clues as to how the virus locks onto the cell membrane.

The retrovirus used by Fass and the team is similar to that which causes leukemia in humans. They hope, with further research, to understand the conformational changes the envelope protein complex undergoes as it works, and to find ways to stop those changes from taking place.

Dr. Debora Fass’ research is supported by the Clore Center for Biological Physics; the Helen and Milton A. Kimmelman Center for Biomolecular Structure and Assembly; and the Leukemia Research Foundation.

Dr. Fass is the incumbent of The Lillian & George Lyttle Career Development Chair.

The Weizmann Institute of Science in Rehovot, Israel, is one of the world’s top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,500 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.

Alex Smith | EurekAlert!
Further information:
http://www.weizmann.ac.il

More articles from Life Sciences:

nachricht Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover

nachricht First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>