Navigation Links
For unzipping DNA mysteries -- literally -- Cornell physicists discover how a vital enzyme works
Date:9/18/2011

ITHACA, N.Y. With an eye toward understanding DNA replication, Cornell researchers have learned how a helicase enzyme works to actually unzip the two strands of DNA. (Nature, online Sept. 18, 2011.)

At the heart of many metabolic processes, including DNA replication, are enzymes called helicases. Acting like motors, these proteins travel along one side of double-stranded DNA, prompting the strands to "zip" apart.

What had been a mystery was the exact mechanics of this vital biological process how individual helicase subunits coordinate and physically cause the unzipping mechanism.

Cornell researchers led by Michelle Wang, professor of physics and an investigator of the Howard Hughes Medical Institute (HHMI), have observed these processes by manipulating single DNA molecules to watch what happens when helicases encounter them, and how different nucleotides that fuel the reactions affect the process. For their experiments they used an E. coli T7 phage helicase, a type with six distinct subunits, which is a good representation of how many helicases work.

"This is a great demonstration of the power of single-molecule studies," said Wang, whose lab specializes in a technique called optical trapping. To record data from single molecules, the scientists use a focused beam of light to "trap" microspheres attached to the molecules.

Prior to this work, researchers from other labs had found that the nucleotide dTTP (deoxythymidine triphosphate) was a "preferred" fuel for the helicase, and that the helicase apparently wouldn't unzip DNA if ATP (adenosine triphosphate) was provided as fuel. Wang and her colleagues found this puzzling, because ATP is known to be the primary fuel molecule in living organisms.

In their latest work, they discovered that, in fact, ATP does cause unwinding, but only in the single-molecule study could they confirm this. In normal biochemical studies, ATP doesn't seem to work, because it causes helicase to "slip" backward on the DNA, then move forward, then slip again.

In bulk studies, rather than single-molecule kinetic observations, the ATP doesn't produce a signal from unwound DNA because the slippage masks the signal.

They then surmised that different mixtures of nucleotides might allow them to investigate helicase subunit coordination. They found that very small amounts of dTTP mixed with large amounts of ATP were enough to decrease the "slippage" events they saw with the ATP alone.

Further inspection revealed that while two subunits of the T7 helicase are binding and releasing nucleotides, the other four can remain bound to nucleotides to anchor the DNA and prevent it from slipping. It only takes one subunit bound to dTTP to decrease slippage almost entirely a little goes a long way.

Such studies can help scientists gain a deeper understanding of helicase mechanics and, in the case of medicine, what happens when helicases go awry or don't bind correctly.

Smita Patel, Rutgers University biochemistry professor and paper co-author, says helicase defects are associated with cancer predisposition, premature aging and many other genetics-related conditions.

"This study provides fundamental new knowledge about a cellular process that is essential to all forms of life," said Catherine Lewis, who oversees single-molecule biophysics grants at the National Institute of General Medical Sciences of the National Institutes of Health. "By using single-molecule methods to study how helicases work, Dr. Wang has resolved several longstanding questions about how the enzyme is coordinated, and possibly regulated, during replication."


'/>"/>

Contact: Blaine Friedlander
bpf2@cornell.edu
607-254-8093
Cornell University
Source:Eurekalert

Related biology news :

1. The sweet mysteries of the nervous system
2. Cold cases gone hot: Montreal researchers solve decades-old medical mysteries using genetics
3. New look at multitalented protein sheds light on mysteries of HIV
4. Extreme archaeology: Divers plumb the mysteries of sacred Maya pools
5. Mexican salamander helps uncover mysteries of stem cells and evolution
6. Unlocking mysteries of the brain with PET
7. Nitrogen mysteries in urban grasslands
8. Zoo volunteers help explain mysteries of the genome
9. Largest ever Alzheimers genome study unveils dementia mysteries
10. Why sleep? UCLA scientist delves into one of sciences great mysteries
11. Journal of General Physiology explores mysteries of TRP channels in latest Perspectives series
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/25/2017)... NEW YORK , Jan. 25, 2017 /PRNewswire/ ... and Access Management (IAM) lifecycle is comprised of ... infrastructure for the purpose of maintaining digital identities ... enterprise resources and applications. There are significant number ... compliance from time to time by optimizing processes ...
(Date:1/23/2017)... Jan. 23, 2017  The latest mobile market research ... have dropped dramatically. The quarterly average price of a ... $276 in Q4 2016.  There are now 120 sub-$150 ... $116, up from just 28 a year ago at ... to Maxine Most , Acuity Market Intelligence Principal, ...
(Date:1/19/2017)... CLARA, Calif. , Jan. 19, 2017 /PRNewswire/ ... company enhancing user experience and security for consumer ... of next-generation payment processing systems and cybersecurity solutions, ... more banks, enterprises and financial institutions worldwide to ... part of the end-to-end secure user authentication platforms ...
Breaking Biology News(10 mins):
(Date:2/20/2017)... ... February 20, 2017 , ... USARAD ... company announces at HIMSS 2017 Annual Conference (Orlando, FL) a world-wide distribution ... a global cloud-based sharing and collaboration platform as part of the Siemens ...
(Date:2/20/2017)... ... February 20, 2017 , ... PuraCath Medical, ... with peritoneal dialysis, announced today that it has published the result of its ... Peritoneal Dialysis International (PDI), the official Journal of the International Society for ...
(Date:2/20/2017)... ORLANDO, Fla. , Feb. 20, 2017 /PRNewswire/ ... (HIMSS) conference in Orlando , ... new offerings, collaborators and clients. IBM Chairman, President ... the HIMSS17 opening keynote address today from 8:30-10 ... www.ibm.com/watson/health , and ibm.com/industries/healthcare. Her remarks examine ...
(Date:2/19/2017)... ... February 19, 2017 , ... Expanding Portfolio to Include ... weighing equipment with the goal of expanding the reach of its quality and ... Starter water analysis meters were introduced into the market in 2014. , The ...
Breaking Biology Technology: