Home > Press > Molecular Motors Cooperate In Moving Cellular Cargo
Tiny movements of molecular motors seen
Molecular Motors Cooperate In Moving Cellular Cargo, Study Shows
Champaign, Ill | April 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 (FIONA). 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."
Collaborators on the study included Illinois graduate students Comert Kural and Hwajin Kim (lead authors), Illinois professor of cell and structural biology Vladimir Gelfand (now at the Northwestern University School of Medicine) and postdoctoral research associates Sheyum Syed at Illinois and Gohta Goshima at the University of California at San Francisco.
The work was funded by the National Institutes of Health, the National Science Foundation, and the U.S. Department of Energy.
James E. Kloeppel
Physical Sciences Editor
Copyright © University of Illinois at Urbana-Champaign
If you have a comment, please Contact
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
A novel method for identifying the body’s ‘noisiest’ networks November 19th, 2014
Researchers discern the shapes of high-order Brownian motions November 17th, 2014
VDMA Electronics Production Equipment: Growth track for 2014 and 2015 confirmed: Business climate survey shows robust industry sector November 14th, 2014
Open Materials Development Will Be Key for HP's Success in 3D Printing: HP can make a big splash in 3D printing, but it needs to shore up technology claims and avoid the temptation of the razor/razor blade business model in order to flourish November 11th, 2014
'Nanomotor lithography' answers call for affordable, simpler device manufacturing October 31st, 2014
Crystallizing the DNA nanotechnology dream: Scientists have designed the first large DNA crystals with precisely prescribed depths and complex 3D features, which could create revolutionary nanodevices October 20th, 2014
Optimum inertial design for self-propulsion: A new study investigates the effects of small but finite inertia on the propulsion of micro and nano-scale swimming machines July 29th, 2014
Breakthrough laser experiment reveals liquid-like motion of atoms in an ultra-cold cluster: University of Leicester research team unlocks insights into creation of new nano-materials July 25th, 2014
Iranian Experts Clean Uranium-Contaminated Water by Nano-Particles November 23rd, 2014
Novel Method Found for Connection of Metallic Alloys to Polymers November 23rd, 2014
New research project supports internationalisation in nano-research: Launch of new “Baltic Sea Network” November 22nd, 2014
3rd Iran-Proposed Nano Standard Approved by International Standard Organization November 22nd, 2014