First crystal structure of intermediate particle in virus assembly created

February 9th, 2009 - 11:48 am ICT by ANI  

London, February 9 (ANI): While viral proteins are known to perform an elegant dance to create infectious structures, American scientists at the Scripps Research Institute claim that they have created the first crystal structure of an intermediate particle they knew was assembled first.
The researchers have revealed that their finding is based on the study of a virus called HK97, which only infects bacteria.
They, however, insist that their study still attains significance because well-known viruses like 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. But this process has never been seen before at this resolution, and now we known that what we thought happens, doesn”t,” Nature magazine quoted the study’’s senior author, Scripps Research Professor John E. Johnson, as saying.
He insisted that deeply understanding how a virus builds its protective coat might help 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 defenceless to antiviral agents,” he said.
The researcher added that knowing how viruses build such vessels to protect the naked viral DNA inside would also be useful in the field of medical nanotechnology.
“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,” he said.
Having solved the structure of the HK97 virus mature outer coat, Johnson and his colleagues revealed that it is made up of 72 protein rings 12 pentagons and 60 hexagons locked together like the chain mail suits worn by knights.
The researchers said that that coating forms the head of the virus, which is extremely small thousands of times narrower than a human hair.
According to them, the crystal structure was very beautiful. They revealed that the proteins that made up the soccer ball-like form were flat in shape and pointed outward, like hands placed palm to palm in prayer.
However, the structure immediately changed shape when it “sensed” the presence of DNA, and 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 said.
While it was previously thought that the proteins went through this motion as a nearly rigid unit, Johnson said that his teams work showed that the proteins significantly changed in structure during the transition.
The researchers have yet to determine whether this structural change happens all at once, or if it moves like a wave around the sphere. (ANI)

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