Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Advance Understanding of Enzyme That Regulates DNA

23.08.2010
Thanks to a single-molecule imaging technique developed by a University of Illinois professor, researchers have revealed the mechanisms of an important DNA regulating enzyme.

Helicase enzymes are best known for “unzipping” DNA for replication, but have many other functions for DNA repair and maintenance. The Illinois team focused on a particular bacterial helicase called PcrA involved in preventing unwanted recombination.

A DNA double helix consists of two strands twisted around each other. When one strand is damaged or breaks, the surrounding area is degraded, leaving a single-stranded region. Specialized proteins then start the process of recombination – rebuilding the second strand using the intact DNA as a template.

“Recombination is essential for DNA repair, but if it runs amok, it causes problems,” said U. of I. physics professor Taekjip Ha. “This helicase controls recombination by removing recombination proteins from the DNA.”

Using a technique called single molecule fluorescence resonance energy transfer (FRET), Ha and his team were able to identify one of the mechanisms that PcrA uses to regulate recombination. The system uses two dyes that change in relative intensity depending on their proximities to one another. The researchers attached the two dyes to the opposite ends of the single-stranded DNA tail.

Helicases are motor proteins, a class of enzymes that use chemical energy to move along a DNA molecule like a train on a track. But using FRET, the researchers observed the two dyes gradually moving closer to each other, then flying apart, repeatedly. Instead of moving along the single-stranded tail, PcrA binds at the point of the break, where the double- and single-stranded regions meet. Then, it uses its motor function to “reel in” the tail, like a fisherman pulling in a rope.

“By combining the structure-specific binding of the enzyme to the DNA and the motor function, the enzyme can reel in the DNA and in the process kick off recombination proteins,” said Ha, who also is a Howard Hughes Medical Institute investigator.

When PcrA reaches the end of its DNA rope, it releases it and starts the reeling in process over again, removing any additional problematic proteins that have bound to the damaged DNA as it reels.

By using FRET, a technique Ha developed, the team also was able to answer another question about PcrA: How consistent is its motor function? Researchers agree that on average, PcrA moves one DNA unit, called a base pair, for each unit of cellular energy it uses, called ATP. But because researchers traditionally study the enzyme in relatively large samples, broad distributions of data have led to conflicting views on whether the helicase moves in uniform steps or those of varying lengths – even up to six base pairs per ATP.

Since FRET is a single-molecule technique, the researchers were able to document a single enzyme’s function, step by step, and found that PcrA does, in fact, move in uniform steps of one base pair per ATP.

Next, the team plans to create a reaction environment more similar to that in vivo, using three and four colors of FRET dyes to measure activities of multiple proteins simultaneously. They are also working toward understanding why helicase moves only in one direction.

“This is an ideal marriage of a new technology and an interesting biological problem,” Ha said.

The team published its findings in the Aug. 20 edition of the journal Cell. Team members included U. of I. graduate students Jeehae Park and Kyung Suk Lee; bioengineering professor Sua Myong; Anita Niedziela-Majka and Timothy Lohman, of the Washington University School of Medicine in St. Louis; and Jin Yu, of the University of California at Berkeley. The National Institutes of Health and the National Science Foundation supported this work.

Liz Ahlberg | University of Illinois
Further information:
http://www.illinois.edu

Further reports about: ATP Advance DNA DNA repair FRET Illinois River Watershed PcrA Regulates Researchers enzyme

More articles from Life Sciences:

nachricht Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>