Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mini cargo transporters on a rat run

27.04.2012
New insight on molecular motor movement

Molecular motors are the key to the development of higher forms of life. They transport proteins, signal molecules and even entire chromosomes down long protein fibers, components of the so-called cytoskeleton, from one location in the cell to another.


Biophysicists of the Technische Universitaet Muenchen and the Ludwig Maximillians Universitaet Muenchen have discovered why some of these transporters can, like cars on a multi-lane motorway, change lanes: The heads of one kinesin (red) have a longer range than the other (blue) which allows "lane change" between the individual fibers (protofilaments) of the microtubule and results in a spiraling movement of the motor on the microtubule. A shorter range of the heads results in a straight movement of the motor. Credit: Melanie Brunnbauer /TU Muenchen

Not unlike trucks on a motorway, there are permanently thousands of these small motor proteins underway at any given point in time – a highly coordinated and extremely fast mode of transport. This highly efficient infrastructure is a prerequisite for the formation of large, complex cells and multicellular organisms. Bacteria, for example, lack this foundation, because they possess neither molecular motors nor cytoskeletons.

Kinesins represent one class of such molecular motors. They run along microtubules comprising 13 individual fibers arranged in a tube form. Kinesins are made up of a twisted pair of protein chains. Each chain comprises a head that can dock to the surface of the microtubules and a neck domain, as well as a stalk and tail domain that the cargo is attached to. Kinesins move forward by placing one head in front of the other in alternation which resembles human walking. The first mechanistically scrutinized kinesin was Kinesin-1, which performs numerous steps in succession without detaching from the microtubule. In the process it moves ahead in a perfectly straight path on its long journey, always remaining on a single fiber of the microtubule.

Scientists led by Zeynep Oekten, group leader at the Biophysics Department of the Technische Universitaet Muenchen, and Melanie Brunnbauer, a doctoral candidate at the Biophysics Department, have now for the first time demonstrated that kinesins also "switch lanes" during transport. The scientists identified the region in the kinesin protein that determines whether a given kinesin type moves on a straight path or in a spiral fashion.

It is a structural element in the neck domain. "If the neck region is stable, the two kinesin heads have only limited reach. The kinesin cannot make any sidesteps and thus moves straight ahead," says Oekten. "However, if the responsible area becomes destabilized, the reach of the heads is increased and the motor protein can jump fibers and spiral around the microtubule."

To confirm this new insight, the scientists integrated specific amino acids into the responsible areas – a kind of molecular switch that allowed them to regulate the reach of the two heads. The result left no doubt: Destabilizing the neck region of the Kinesin-1 motor increases the reach of the two heads, which in turn causes the Kinesin-1 to depart from its normally perfectly straight path and move along a spiral-shaped path. When they mimicked a stable neck region using a chemical crosslinker, they coerced the protein into running straight again.

Oekten and Brunnbauer arrived at their new insight using a unique experimental setup. They placed two 3-micron large synthetic beads in a solution and trapped each using a laser beam, a so-called pair of "optical tweezers." Then, in precision work, they placed a piece microtubule between the beads. In a final step, again using a laser beam, they trapped a third bead coated with a specific type of kinesin and carefully placed it onto the microtubule.

As soon as they deactivated the third laser beam, the motor protein started marching forward and the scientist could follow the path of the molecule under the microscope. "In this way we were able, for the first time ever, to directly observe the spiraling movement of a motor type," explains Oekten. "When we saw the teetering movement of a Kinesin-2 protein for the first time, we all laughed. The motion was so clear and obvious, you just had to look at it and all doubt vanished." The experimental setup allows the molecular motors to move freely, thereby emulating real-life conditions in the cell much better than previous methods of investigation.

Using their new experimental setup, Oekten and Brunnbauer investigated a whole series of different Kinesin-2 proteins from various organisms – with an unexpected result: Contrary to the hitherto prevalent assumption that kinesins typically move only on straight paths, almost all kinesins displayed some form of spiral movement, in manifold variations. "This shows us that spiral motion is not an exception in nature, but rather the rule," explains Oekten. "In fact, the more relevant question is why evolution has brought about the straight-line movement as we observe with the Kinesin-1. That is truly unusual considering the nano-scale precision it requires to confine a kinesin transporter on an exclusively straight path." The researchers Oekten and Brunnenbauer hope to more closely investigate the reasons for the various kinds of motion in the future.

The research was funded by the Deutsche Forschungsgemeinschaft (DFG, SFB 863). In the publication, the authors extend special thanks to Brunnbauer's baby son Benedikt and his babysitter Christine Wurm. In the Biophysics Department, Melanie Brunnbauer found the flexibility and support she needed to continue her work following the birth of her son. Her success provides the proof that family and cutting-edge research are not mutually exclusive – given the right conditions.

Dr. Andreas Battenberg | EurekAlert!
Further information:
http://www.tum.de

More articles from Physics and Astronomy:

nachricht NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center

nachricht Pluto's hydrocarbon haze keeps dwarf planet colder than expected
16.11.2017 | University of California - Santa Cruz

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>