Crammed with charged DNA, pressure rises inside virus

Jun 05, 2007
Crammed with charged DNA, pressure rises inside virus
Image credit: Ye Xiang and Michael Rossmann, Purdue University.

It could be an artist’s depiction of someone’s stomach before and after a rather decadent meal. But it is a 3-D cryoelectron microscope reconstruction of the cross-section of a virus, before and after cramming itself full of its own DNA.

The virus, phi29, has a tiny motor that pumps its DNA into the capsid—outer shell—during the assembly process. The potential energy of the tightly coiled DNA may help phi29 inject its genetic material into the bacterial cells it infects.

Now a team led by physicists at the University of California, San Diego has used laser tweezers to measure the forces exerted by the motor as it pushes the DNA into the capsid.

“The virus’ motor has to do mechanical work to overcome two factors that create resistance,” said Douglas Smith, an assistant professor of physics at UCSD who headed the team that published the discovery this week in the early on-line edition of Proceedings of the National Academy of Sciences. “First, the DNA must be forced to bend. Second, the electrostatic repulsion of the DNA’s negatively charged backbone must be overcome. We found that the positively charged ions in the solution are critical to overcoming this repulsion. Without the right combination of positively charged ions, the virus could not force all of its DNA into the capsid.”

The researchers discovered that the forces in the capsid are slightly higher than predicted by theoretical calculations. They say this may be because the packed DNA is less ordered than assumed in the calculations.

Source: University of California - San Diego

Explore further: Diabetes drug found in freshwater is a potential cause of intersex fish

Related Stories

Genes tell story of birdsong and human speech

Dec 11, 2014

His office is filled with all sorts of bird books, but Duke neuroscientist Erich Jarvis didn't become an expert on the avian family tree because of any particular interest in our feathered friends. Rather, ...

Work on pioneering pan-European neutron facility underway

Oct 21, 2014

A state-of-the-art facility capable of generating neutron beams 30 times brighter than current facilities is about to be constructed in the Swedish town of Lund. The EUR 1.8 billion will help scientists examine ...

New functions for chromatin remodelers

Aug 28, 2014

Large molecular motors consisting of up to a dozen different proteins regulate access to the genome, which is essential for the transcription of genes and for the repair of DNA damage. Susan Gasser and her ...

Relaxation helps pack DNA into a virus

May 26, 2014

Researchers at the University of California, San Diego have found that DNA packs more easily into the tight confines of a virus when given a chance to relax, they report in a pair of papers to be published ...

Recommended for you

York's anti-malarial plant given Chinese approval

Apr 24, 2015

A new hybrid plant used in anti-malarial drug production, developed by scientists at the University of York's Centre for Novel Agricultural Products (CNAP), is now registered as a new variety in China.

The appeal of being anti-GMO

Apr 24, 2015

A team of Belgian philosophers and plant biotechnologists have turned to cognitive science to explain why opposition to genetically modified organisms (GMOs) has become so widespread, despite positive contributions ...

Micro fingers for arranging single cells

Apr 24, 2015

Functional analysis of a cell, which is the fundamental unit of life, is important for gaining new insights into medical and pharmaceutical fields. For efficiently studying cell functions, it is essential ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.