We might have enjoyed a day off from our jobs this Labor Day, but our cellular workers never rest. While you relaxed at the beach or fired up the grill, mitochondria generated your cells' power supplies, lysosomes took out the trash and ribosomes churned out proteins that'll go on to do even more tasks.
Other microscopic employees, microtubules, will work many jobs. These strong protein filaments make up part of the cell’s skeleton and serve as tracks for shuttling internal cargo. When cells divide, it’s microtubule fibers that physically pull the chromosomes into each daughter cell. And on some cell exteriors, microtubules form long, waving hairs that sweep mucus from the lungs or guide eggs toward the uterus.
Microtubules perform these important tasks by repeatedly growing and shrinking. In this animation, proteins called tubulin snap into place like Lego blocks to build a microtubule. When construction ends, the hollow cylinder immediately shortens as it falls to pieces.
Until recently, scientists didn’t know exactly what drove microtubules to fall apart. A National Institutes of Health-funded research team led by Eva Nogales of the Lawrence Berkeley National Laboratory and the University of California, Berkeley, now has an explanation. Using high-powered microscopy, the scientists peered into the structure of a microtubule and found how a chemical reaction puts the stacking tubulin proteins under intense strain. The only thing keeping them from springing apart is the pressure from the addition of more tubulin. So when elongation ends, the microtubule deconstructs.
The team also learned that Taxol, a common cancer drug, relieves the pressure and allows microtubules to remain intact indefinitely. With microtubules frozen in place, a cancer cell cannot multiply and eventually dies.
Because of this research, scientists now better understand both a widely used anticancer agent and one of our toughest cellular laborers.
The research reported in this article was funded in part under NIH grant P01GM051487.
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