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.
European roadmap for graphene science and technology published February 25th, 2015
Quantum research past, present and future for discussion at AAAS February 16th, 2015
World’s first compact rotary 3D printer-cum-scanner unveiled at AAAS by NTU Singapore start-up: With production funded by crowdsourcing, the first unit will be delivered to the United States in March February 16th, 2015
Nanotechnology Electric Vehicle (EV) Market Analysis Report 2015: According to Radiant Insights, Inc February 13th, 2015
Monitoring the real-time deformation of carbon nanocoils under axial loading February 18th, 2015
Stomach acid-powered micromotors get their first test in a living animal January 27th, 2015
Nanoshuttle wear and tear: It's the mileage, not the age January 26th, 2015
Mysteries of ‘Molecular Machines’ Revealed: Phenix software uses X-ray diffraction spots to produce 3-D image December 22nd, 2014
Graphene Shows Promise In Eradication Of Stem Cancer Cells March 1st, 2015
Novel Method to Determine Optical Purity of Drug Components March 1st, 2015
Scientific breakthrough in rechargeable batteries: Researchers from Singapore and Québec Team Up to Develop Next-Generation Materials to Power Electronic Devices and Electric Vehicles February 28th, 2015
First detailed microscopy evidence of bacteria at the lower size limit of life: Berkeley Lab research provides comprehensive description of ultra-small bacteria February 28th, 2015