Navigation Links
The connector rotation hypothesis? Phage do not pack their DNA by rotation

The life cycles of many viruses include a self-assembly stage in which a powerful molecular motor must pack the DNA genome into the virus's preformed shell (the capsid). How it manages this intricate feat has been subject to debate, but we know that the DNA passes into the capsid shell through a channel formed by a structure called the connector. Scientists have speculated that rotation of the connector complex might feed the DNA into the capsid as it turns.

In a new study published online this week in the open access journal PLoS Biology, researchers Thorsten Hugel, Jens Michaelis, Craig Hetherington, and Carlos Bustamante present their detailed investigation into how the Bacillus subtilis bacteriophage ö29 crams its DNA into the capsid following replication.

Using their innovative system, Hugel and colleagues were able to observe capsids as they pack their DNA to directly test the connector rotation hypothesis. They found that it is more than likely not the mechanism by which the DNA is packed. The researchers combined single-molecule fluorescence polarization with "magnetic tweezers" to glue the end of the capsid farthest from the hole to a slide using antibodies, and then they draw out the DNA being packaged in the opposite direction by attaching a magnetic bead to its loose end and applying a magnetic field. Importantly, they also labeled the connector complex with fluorescent dye molecules so they could observe its motion using single-molecule fluorescence polarization spectroscopy.

The researchers then looked at connector movement during DNA packaging in six ö29 mutants. After attaching the fluorescent molecules to the connector complex, they set the mutants to work packaging DNA in a flow chamber. As the connectors functioned, the researchers shone homogeneously polarized light on them and recorded the pattern of fluorescence produced in two channels at right angles to one other.

If the connectors had been rotating, the y would have seen a sine wave-like fluctuation in intensity in both channels with a phase shift of 90 degrees. They did not see the sine waves, and mathematical analysis of the fluorescence pattern confirmed that the changes in the fluorescence emitted by the molecules as packaging took place did not correspond to any sort of continuous rotational motion. The researchers concluded with more than 99% certainty that the packaging mechanism does not involve rotation.

How, then, does it happen? The researchers noted that their findings are compatible with a recently proposed nonrotating model in which the ring of ATPases alternately compresses and extends, drawing in the DNA. But further testing will be needed to confirm the validity of that model to the degree of certainty with which this team rejected the rotator hypothesis.


'"/>

Source:Public Library of Science


Related biology news :

1. Priming embryonic stem cells to fulfill their promise
2. Protein offers way to stop microscopic parasites in their tracks
3. Flocking together: Study shows how animal groups find their way
4. Where bacteria get their genes
5. Chickadees can help humans get their bearings
6. Bacteria use hosts immune response to their competitive advantage
7. Structures of marine toxins provide insight into their effectiveness as cancer drugs
8. Beauty queens urge girls not to sacrifice their bones
9. Researchers learn how blood vessel cells cope with their pressure-packed job
10. Stem cells electric abilities might help their safe clinical use
11. Multiple genes permit closely related fish species to mix and match their color vision
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:4/28/2016)... BANGALORE, India , April 28, 2016 /PRNewswire/ ... product subsidiary of Infosys (NYSE: INFY ), and ... global partnership that will provide end customers with ... banking and payment services.      (Logo: http://photos.prnewswire.com/prnh/20130122/589162 ... area for financial services, but it also plays a fundamental ...
(Date:4/19/2016)... DUBAI , UAE, April 20, 2016 ... can be implemented as a compact web-based "all-in-one" system ... in the biometric fingerprint reader or the door interface ... requirements of modern access control systems. The minimal dimensions ... the ID readers into the building installations offer considerable ...
(Date:4/13/2016)... physicians supporting Medicaid patients in Central Florida ... telehealth thanks to a new partnership with higi.   ... can routinely track key health measurements, such as blood ... they opt in, share them with IMPOWER clinicians through ... location at no cost. By leveraging this data, IMPOWER ...
Breaking Biology News(10 mins):
(Date:5/23/2016)... Holly Springs, North Carolina (PRWEB) , ... May ... ... comprehensive process automation and building management solutions and services based in Aurora, Ohio, ... a decade of established business in the Research Triangle Park area, this new ...
(Date:5/22/2016)... (PRWEB) , ... May 22, 2016 , ... Doctors in ... in combating the asbestos cancer, malignant mesothelioma. Surviving Mesothelioma has just posted an article ... in the University of Rome’s Department of Clinical Sciences and Translational Medicine evaluated more ...
(Date:5/20/2016)... (PRWEB) , ... May 20, 2016 , ... Kablooe Design, ... goods companies, today announced its official 25th anniversary of the business. “We have worked ... so grateful to our customers for the privilege and honor of serving their product ...
(Date:5/20/2016)... ... ... The recent recall by Costco and Trader Joes of 47 million pounds of ... demonstrates the need for faster and more cost effective bio-threat detection to ensure food ... , PathSensor’s latest solution uses a biosensor technology called CANARY®. CANARY®, an ...
Breaking Biology Technology: