Scientists explore the mechanisms of viruses' shells

Dec 10, 2013
Representation of a viral capsid. The yellow dots mark the edges of the mechanic ‘tiles’ Credit: SISSA

The genome of viruses is usually enclosed inside a shell called capsid. Capsids have unique mechanic properties: they have to be resistant and at the same time capable of dissolving in order to release the genome into the infected cell. The scientists of the International School for Advanced Studies (SISSA) of Trieste have coordinated a study on the mechanic properties of viruses that have improved their understanding, so much that they were able to make conjectures on the behavior of still little-known viruses.

Viruses are like small vessels containing an active component, the genetic material, that can infect a host cell. The vessel, called capsid or vector, is basically a shell that changes its shape when it penetrates a cell to infect it, and may even break into pieces. The research team, that includes Guido Polles and Cristian Micheletti of SISSA, carried out computer simulations and used theoretical models to understand how such 'vessel' responds to thermal and mechanic stimulations. In such a way they identified the weak points of and inferred their spontaneous assembly process.

Each shell is made of numerous protein 'tiles' that spontaneously join up like Lego pieces. A capsid may be composed of hundreds of such subunits, but each 'tile' consists of a limited number of proteins. The edges of the tiles are the "weak" lines where the deformation of the general structures takes place and along which the shell fragments if broken. Experimental observations have been carried out for some types of viruses to understand the internal dynamic of the vector (deformation) and the shape of the single tiles (which is usually rather regular - pentagons, hexagons, triangles). Micheletti and his colleagues produced a virtual model that, in principle, may be applied to any virus whose structure is known.

"Starting from the available information on the molecular structure of the capsid, we tried to 'tease' it a little to see the way it changed its shape. By simulating thermal fluctuations (to put it more simply, we virtually heated and then cooled it) observing along which lines the would modify. It is very likely that these very lines are also the spots in which the capsid will tend to break up." explained Polles and Micheletti. "Our model turned out to be very robust. The simulations, in fact, reproduced the same conditions observed in the experiments on known capsids. For this reason we have made other speculations on capsids on which we have no direct knowledge in this sense."

The research, carried out alongside with University of York (UK), Università di Torino and the Max Planck Institute of Mainz (Germany), was published in Plos Computational Biology. The studies on the nature of viral capsids are important to understand the mechanisms of virus infection (and to study methods to fight it).

Viral vectors, besides, are used in pharmacology and in gene therapy. The ' shells in fact may be employed as vectors to insert a therapy directly into cells, a cutting-edge methodology in today's medicine. Being able to identify the mechanically weak spots may be exploited, in perspective, to modify the natural capsids optimizing their resilience to convey and deliver the pharmacologic content more effectively.

Explore further: Scientists find the invisibility cloak that shields HIV-1 from the immune system

More information: Guido Polles, G Indelicato, R Potestio, P Cermelli, R Twarock, C Micheletti, "Mechanical and Assembly Units of Viral Capsids Identified via Quasi-Rigid Domain Decomposition"November 14, PLOS Computational Biology 2013DOI: 10.1371/journal.pcbi.1003331

add to favorites email to friend print save as pdf

Related Stories

Viruses are as simple as they are "smart"

Nov 25, 2013

Viruses are as simple as they are "smart": too elementary to be able to reproduce by themselves, they exploit the reproductive "machinery" of cells, by inserting pieces of their own DNA so that it is transcribed ...

Team discovers new form of virus reproduction

Oct 17, 2013

Each small step that Science takes to discover how viruses infect cells is always very valuable to researchers and society, since it provides relevant information to fight infections.

Do-it-yourself viruses: How viruses self assemble

Dec 16, 2012

A new model of the how the protein coat (capsid) of viruses assembles, published in BioMed Central's open access journal BMC Biophysics, shows that the construction of intermediate structures prior to fin ...

Image pinpoints all 5 million atoms in viral coat

Feb 16, 2009

(PhysOrg.com) -- If a picture is worth a thousand words, then Rice University's precise new image of a virus' protective coat is seriously undervalued. More than three years in the making, the image contains ...

Recommended for you

Molecular gate that could keep cancer cells locked up

7 hours ago

In a study published today in Genes & Development, Dr Christian Speck from the MRC Clinical Sciences Centre's DNA Replication group, in collaboration with Brookhaven National Laboratory (BNL), New York, ...

The 'memory' of starvation is in your genes

10 hours ago

During the winter of 1944, the Nazis blocked food supplies to the western Netherlands, creating a period of widespread famine and devastation. The impact of starvation on expectant mothers produced one of the first known ...

Sugar mimics guide stem cells toward neural fate

Jul 30, 2014

Embryonic stem cells can develop into a multitude of cells types. Researchers would like to understand how to channel that development into the specific types of mature cells that make up the organs and other structures of ...

User comments : 0