Navigation Links
Scripps scientists create first crystal structure of an intermediate particle in virus assembly
Date:2/8/2009

The structure, described February 8 in an advance online publication of the journal Nature, provides fresh insights into the elegant dance that viral proteins perform to create the infectious structure that causes all manner of misery and disease, say researchers. While the virus they studied, HK97, only infects bacteria, well-known viruses such as herpes and HIV are also known to assemble an "intermediary" structure before morphing into its final assault-proof, infectious form.

"The principles of this multi-stage protein coat assembly will likely be similar across all complex viruses," says the study's senior author, Scripps Research Professor John E. Johnson. "But this process has never been seen before at this resolution, and now we known that what we thought happens, doesn't."

That's important, Johnson says, because if scientists understand how a virus builds its protective coat, they may be able to medically target vulnerabilities in the first stage of that assembly. "We believe that without its final shell to protect it, an immature virus will be much more defenseless to antiviral agents," he says.

Knowing how viruses build these vessels to protect the naked viral DNA inside is also useful in the field of medical nanotechnology, he adds. "The immature coat has lots of holes in it through which we could load drugs, and then seal it in the mature form to produce a potent delivery system," Johnson says.

Johnson and his research team have long studied HK97, and had "solved" the structure of the virus's mature outer coat. It is made up of 72 protein rings 12 pentagons and 60 hexagons locked together like the chain mail suits worn by knights. This coating forms the head of the virus, which is extremely small thousands of times narrower than a human hair.

The thin viral armor offers protection and stability as well as freedom of movement, Johnson says. "This is a container that works very well."

But the researchers say they spent five "painful" years trying to produce a crystal structure of the intermediate particle they knew was assembled first. They had produced images using electron microscopy, but they weren't detailed enough to understand the molecular processes involved.

The scientists built the viral shells in a test tube. Genes that encode the 420 proteins that make up the coat were expressed in e coli bacteria, the normal host of the virus. These proteins spontaneously assemble and form the immature particles. In the presence of viral DNA and the enzymes that pump it into the particles, they instantly form a mature coat that engulfs the genes.

The study's first author, Ilya Gertsman, a researcher in Johnson's lab, kept trying to capture the crystal structure of the intermediate form of the virus, but it always quickly morphed into its final armored form, even without DNA present. Finally, working with collaborators from the University of Pittsburgh, Gertsman used a form of HK97 that was mutated in such a way that made it slow to mature.

What the researchers saw from the crystal structure "was so beautiful," Gertsman says. The proteins that made up the spherical, soccer ball-like form were flat in shape and pointed outward, like hands placed palm to palm in prayer. But the moment the structure "sensed" the presence of DNA it immediately changed shape. In essence, the fingers on the praying hands folded down together, fingers interspersed and grasping each other. "That's why the final protein coat is so stable. The proteins are all intertwined around each other," Johnson says. Previously it was thought that the proteins went through this motion as a nearly rigid unit. This study showed that the proteins significantly changed in structure during the transition. The researchers don't yet know if this structural change happens all at once, or if it moves like a wave around the sphere.

They hypothesize that domains that hang from each of the proteins that eventually form the viral coat drive the process of changing the structure. The tails interact with each other to distort the shape of the proteins, Johnson says. "As long as the tails are there, the process of change is reversible. When the tails are gone (removed by a viral enzyme), the structure becomes stable," he says. Researchers had thought these tails, which are scaffolding proteins, guided assembly of the particle "but we think they actually change the structure," Johnson says. "That offers us another target by which we may be able to interrupt assembly of the coat."


'/>"/>

Contact: Keith McKeown
kmckeown@scripps.edu
858-784-8134
Scripps Research Institute
Source:Eurekalert

Related biology news :

1. Scripps scientists develop first examples of RNA that replicates itself indefinitely
2. Scripps Research scientists shed light on how DNA is unwound so that its code can be read
3. Dolphin population stunted by fishing activities, Scripps/NOAA study finds
4. Scripps research team defines new painkilling chemical pathway
5. Scripps research scientists identify blood component that turns bacteria virulent
6. Scripps research scientists identify compounds for stem-cell production from adult cells
7. Scripps Florida scientists awarded $1.5M to fight major water and food parasites
8. Scripps research team sheds light on immune system suppression
9. Scripps research team solves structure of beneficial virus
10. Oceans on the precipice: Scripps scientist warns of mass extinctions and rise of slime
11. Scripps scientists will assess Beijing Olympics air pollution control efforts
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/2/2016)... June 2, 2016   The Weather Company , an ... Ads, an industry-first capability in which consumers will be able ... to ask questions via voice or text and receive relevant ... Marketers have long sought an advertising solution ... can be personal, relevant and valuable; and can scale across ...
(Date:6/1/2016)... Favorable Government Initiatives Coupled With ... Identification to Boost Global Biometrics System Market Through 2021  ... report, " Global Biometrics Market By Type, By ... 2011 - 2021", the global biometrics market is projected ... of growing security concerns across various end use sectors ...
(Date:5/20/2016)... May 20, 2016  VoiceIt is excited to ... VoicePass. By working together, VoiceIt and ... VoiceIt and VoicePass take slightly different approaches to ... both security and usability. ... this new partnership. "This marketing and ...
Breaking Biology News(10 mins):
(Date:11/30/2016)... GREENWICH, Connecticut , November 30, 2016 ...   ... Aptuit, LLC today announced ... screening library. An additional 150,000 novel compounds have increased the ... selected to broaden the hit discovery capabilities of the company. ...
(Date:11/30/2016)... ... November 30, 2016 , ... ... technology applications, introduces the 5th generation, ultra-bright, Laser-Driven Light Source, the EQ-77, at ... Source (LDLS™) technology, the EQ-77 offers higher radiance and irradiance from a truly ...
(Date:11/30/2016)... ... , ... With growth rates averaging more than 30% each year, Random42 has ... continuing their expansion in their new office space. The new office has a fantastic ... the creative industries, so Random42 Scientific Communication will fit right in. , Ben ...
(Date:11/30/2016)... November 30, 2016 Teil einer ... ... , Aptuit LLC ... zu haben. Zusätzliche 150.000 neuartige Substanzen haben die Prüfsammlung ... ausgewählt, um die starken Entdeckungsfähigkeiten des Unternehmens zu erweitern. ...
Breaking Biology Technology: