Molecular motors cooperate in moving cellular cargo, study shows

Apr 07, 2005

Researchers using an extremely fast and accurate imaging technique have shed light on the tiny movements of molecular motors that shuttle material within living cells. The motors cooperate in a delicate choreography of steps, rather than engaging in the brute-force tug of war many scientists had imagined.

"We discovered that two molecular motors -- dynein and kinesin -- do not compete for control, even though they want to move the same cargo in opposite directions," said Paul Selvin, a professor of physics at the University of Illinois at Urbana-Champaign and corresponding author of a paper to appear in the journal Science, as part of the Science Express Web site, on April 7. "We also found that multiple motors can work in concert, producing more than 10 times the speed of individual motors measured outside the cell."

Dynein and kinesin are biomolecular motors that haul cargo from one part of a cell to another. Dynein moves material from the cell membrane to the nucleus; kinesin moves material from the cell nucleus to the cell membrane. The little cargo transporters accomplish their task by stepping along filaments called microtubules.

To measure such minuscule motion, Selvin and colleagues at Illinois developed a technique called Fluorescence Imaging with One Nanometer Accuracy. The technique can locate a fluorescent dye to within 1.5 nanometers (one nanometer is a billionth of a meter, or about 10,000 times smaller than the width of a human hair). Recent improvements to FIONA now allow scientists to detect motion with millisecond time resolution.

Selvin's team used FIONA to track fluorescently labeled peroxisomes (organelles that break down toxic substances) inside specially cultured fruit fly cells. This was the first time the imaging technique had been used inside a living cell.

"Our measurements show that both dynein and kinesin carry the peroxisomes in a step-by-step fashion, moving about 8 nanometers per step," said Selvin, who also is a researcher at the Frederick Seitz Materials Research Laboratory on the Illinois campus.

"Because we see a fairly constant step size, we don't believe a tug of war is occurring," Selvin said. "If the dynein was fighting the kinesin, we would expect to see a lot of smaller steps as well."

The researchers also noted that faster movements occurred with the same step size, but with greater rapidity. When measured outside the cell, kinesin moved about 0.5 microns per second. Inside the cell, the speed increased to 12 microns per second.

"There must be a mechanism that allows the peroxisomes to move by multiple motors much faster than independent, uncoupled kinesins and dyneins," Selvin said. "It appears that motors are somehow regulated, being turned on or off in a fashion that prevents them from simultaneously dragging the peroxisome."

In the future, Selvin wants to combine FIONA and an optical trap technique to monitor the speed and direction of a peroxisome, and the force acting upon it.

"By measuring force we can determine how many molecular motors are working together," Selvin said. "This will help us further understand these marvelous little machines."

Source: University of Illinois at Urbana-Champaign

Explore further: How we can substitute critical raw materials in catalysis, electronics and photonics

add to favorites email to friend print save as pdf

Related Stories

Creating the energy Internet

33 minutes ago

It only takes a power outage of a few minutes in the middle of a busy workday to drive home the hazards of relying on an energy infrastructure rooted in the Industrial Age. Without the electricity delivered ...

Baby sea turtles starved of oxygen by beach microbes

33 minutes ago

On a small stretch of beach at Ostional in Costa Rica, hundreds of thousands of sea turtles nest simultaneously in events known as arribadas. Because there are so many eggs in the sand, nesting females freque ...

Forest tree seeds stored in the Svalbard seed vault

23 minutes ago

A new method for the conservation of the genetic diversity of forest trees will see its launch on 26 February 2015, as forest tree seeds are for the first time stored in the Svalbard Global Seed Vault on the Spitsbergen Island, ...

SatisFactory project for more attractive factories launched

35 minutes ago

Known as either "Industrial Revolution 4.0" or as "Industrial Renaissance", the need for visionary industrial approaches is widely recognized in the European Union. SatisFactory, a three-year research project funded by the ...

Recommended for you

Semiconductor miniaturisation with 2D nanolattices

Feb 26, 2015

A European research project has made an important step towards the further miniaturisation of nanoelectronics, using a highly-promising new material called silicene. Its goal: to make devices of the future ...

Ultra-small block 'M' illustrates big ideas in drug delivery

Feb 26, 2015

By making what might be the world's smallest three-dimensional unofficial Block "M," University of Michigan researchers have demonstrated a nanoparticle manufacturing process capable of producing multilayered, precise shapes.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.