HOUSTON -- (Nov. 5, 2010) -- A new study by Rice University bioengineers finds that the workhorse proteins that move cargo inside living cells behave like prima donnas. The protein, called kinesin, is a two-legged molecular machine. Rice's scientists invented tools that could measure the pulling power of kinesin both singly and in pairs, and they report this week in Biophysical Journal that kinesins don't work well together -- in part because they are so effective on their own.
"Researchers have been investigating the mechanical properties of individual motor proteins for some time now, but this is the first time anyone's been able to tie a defined number of molecular motors to a cargo and watch them work together," said lead researcher Michael Diehl, assistant professor in bioengineering at Rice. "We know that more than one of these motors is attached to most cargoes, so understanding how they work together -- or fail to -- is a key to better understanding the intracellular transport system."
Cargoes inside cells are hitched to teams of motor proteins and hauled from place to place like horse-drawn wagons. Like stagecoaches or wagons, many cargoes are pulled by several horses. But unlike a wagon, cellular cargoes often also have multiple teams pulling in opposite directions.
"Motor proteins move directionally," Diehl said. "They either move toward the cell's nucleus or they move away from the nucleus toward the periphery. Grouping different types of motors together allows cells to regulate cargo movement. But when there are multiple motors pulling antagonistically in opposite directions, what determines which group wins? What influences the balance? How do they cooperate or compete to get the right packages to the right place? Those are the kinds questions we're trying to answer."
Diehl said intracellular transport has become an increasingly hot topic over the past decade, in part because researchers have found that
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