Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tiny molecular motors shed light on cell function, say Stanford researchers

05.03.2004


Every cell in the body has what James Spudich, PhD, calls "a dynamic city plan" comprised of molecular highways, construction crews, street signs, cars, fuel and exhaust. Maintenance of this highly organized structure is fundamental to the development and function of all cells, Spudich says, and much of it can be understood by figuring out how the molecular motors do the work to keep cells orderly.



Spudich, biochemistry professor at the Stanford University School of Medicine, and Stanford physics graduate student David M. Altman report in the March 5 issue of Cell how a type of molecular motor provides the rigidity needed by the tiny sensors in the inner ear in order to respond to sound. They found that this motor creates the proper amount of tension in the sensors and anchors itself to maintain that tension.

"Our general feeling is that tension-sensitive machines are at the heart of the dynamic city plan," said Spudich. Their National Institutes of Health-funded study has implications far beyond how an obscure molecule provides rigidity for a protein in the inner ear. A motor able to create structural changes by taking up slack in proteins and clamping down so that they remain in a rigid position may help explain many intricacies of cellular organization, such as how chromosomes line up and separate during cell division.


"Studies like this allow you to understand enough details of these motors to design small molecules to affect their function," said Spudich, who is also the Douglass M. and Nola Leishman Professor of Cardiovascular Disease. Toward this end he has co-founded a company, Cytokinetics, in hopes of creating drugs that selectively target molecular motors involved in cancer and cardiovascular disease.

For years, Spudich’s lab has studied molecular motors called myosins, proteins that carry out cellular motion by attaching to and "walking" along fibers of actin. The interaction of actin and myosin is the mechanism behind cell actions such as muscle contractions, the pinching off of two daughter cells from a mother cell during division and the hauling of cargo molecules around in a cell. Of the 18 types of myosin molecules, their current findings examine myosin VI, thought to be responsible for setting the tension for stereocilia, actin-filled rods on the sound-sensing hair cells of the inner ear. A defect in myosin VI results in deafness.

Although it was known that myosin moves along actin fibers, it had never previously been demonstrated how myosin could function as an anchor or a clamp. To study this, Spudich and Altman needed techniques beyond the realm of biology. "This is a problem for physicists who think in terms of forces and putting a load on a system," said Spudich. Altman specializes in optical tweezers, a focused laser that allows the manipulation of microscopic beads, and provided the required physics know-how by applying his expertise to studying myosin activity precisely.

The Cell paper includes a number of complex equations describing how the myosin VI anchor works, but the researchers have easily simplified the concept: think of the palm of an open hand as the hair cell and the fingers as the stereocilia. Myosin VI has two legs as well as a tail, which can bind to other things. The researchers think the myosin VI tail in the hair cell binds to the webbing between the fingers - the cell membrane between the stereocilia - and then as the legs walk across the palm (the hair cell) it pulls the webbing between the fingers taut which makes the stereocilia rigid.

As the motor continues walking, the taut membrane strains the motor and distorts its shape, which turns the motor into an anchor. If the webbing/membrane becomes slack again, the motor regains its normal shape and begins walking again. It continues walking until the membrane becomes taut again.

"You can imagine that if a motor like this didn’t stall, it would end up continuing to burn energy in the cell and would keep pulling this membrane, but it would be wasting a lot of energy," said Altman, who is first author of the paper. "So this change has made it a smart and efficient motor."

"The sophistication of what David has been able to do here in terms of looking at a single molecule and how it behaves is unusual," Spudich noted. "There are very few proteins in biology that have been analyzed and understood down to this level." Altman is now looking at defective myosin VI that causes deafness in hopes of learning even more about the precise refinement of the molecular motor.


Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children’s Hospital at Stanford. For more information, please visit the Web site of the medical center’s Office of Communication & Public Affairs at http://mednews.stanford.edu.

Mitzi Baker | EurekAlert!
Further information:
http://mednews.stanford.edu

More articles from Life Sciences:

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

nachricht Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>