In a new study, researchers at the University of Illinois and Columbia University report on how a key motor protein orchestrates chromosome movements at a critical stage of cell division.
The study appeared in the Proceedings of the National Academy of Sciences.
Within the complex world of the cell, motor proteins function as a kind of postal service. These proteins carry cargo from one location to another in the cell, a job that requires precision, in both the location and the timing of delivery. They are fueled by a small molecule, adenosine tri-phosphate (ATP).
Some motor proteins are essential to mitosis – the process by which cell division occurs in higher organisms. During cell division it is important for chromosomes to line up at the middle of the parent cell allowing for their separation between the two daughter cells.
Motor proteins play a key role in the movement of chromosomes to and from the poles of the cell. Should any of these processes lose coordination, it could result in disease or cell death.
How chromosomes move during cell division is a question that is fundamental to biology and is of importance in understanding many diseases. University of Illinois physics professor Paul Selvin and his colleagues focused on a motor protein, centromeric protein E (CENP-E) that is known to be associated with chromosomes.
“The question is whether CENP-E acts like a transporter or like an anchor,” Selvin said.
“A transporter moves things around the cell, whereas an anchor sits someplace in the cell, holds onto something, and causes the thing to be held down,” Selvin said. “It turns out CENP-E is known to be an anchor, but is it also a transporter?”
Earlier studies had established a role for CENP-E in aligning paired chromosomes. This alignment is important for ensuring that one of each pair makes its way into a different daughter cell.
CENP-E is part of a large class of proteins called kinesins. These motor proteins walk across the cell on special tightropes, called microtubules, using ATP as an energy source.
“The motion of ’normal‘ kinesin, kinesin-1, is now well known,” Selvin said. “It turns out it’s like a little person – it walks with its two feet, one in front of the other. I was interested to know whether the normal rules of how kinesin walks apply to these different kinds of kinesins.”
“In vivo studies are hampered by the presence of lots of other proteins, making it hard to study how much a single protein moves, how fast it moves and how much force it produces,” said Hasan Yardimci, a post doctoral researcher in Selvin's lab and lead author on the study.
Instead, Yardimci used a technique that allowed him to look at one molecule at a time.
The most direct way to measure how a protein moves is to watch it in real time. Using special molecular bulbs called quantum dots, which light up the protein, Yardimci was able to watch CENP-E move along its microtubule tightrope. By resolving these motions on the nanometer scale, he was able to make two key observations.
“The protein takes eight nanometer steps in a hand-over-hand fashion,” Yardimci said. The protein moved in a direction consistent with the way chromosomes move within cells, over lengths that are normally observed during cell division.
To test the kind of loads that CENP-E could withstand, Yardimci set up a tug of war between a micron-sized bead and the protein. As the protein moved, it pulled on the bead.
By measuring the force on the bead, the researchers were able to calculate how much force CENP-E could exert.
The observation that CENP-E shares several common features with kinesin-1 provides insights into its molecular workings.
“We showed that it is likely that CENP-E moves chromosomes around,” Selvin said. “That is, we showed that it is a transporter in vitro, hauling around a little bead. Now we need to do it in vivo, on chromosomes.”
The research team included Steven Rosenfeld at Columbia University.
Kaushik Ragunathan | University of Illinois
Russian scientists show changes in the erythrocyte nanostructure under stress
22.02.2019 | Lobachevsky University
How the intestinal fungus Candida albicans shapes our immune system
22.02.2019 | Exzellenzcluster Präzisionsmedizin für chronische Entzündungserkrankungen
An international research team including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has combined radio telescopes from five continents to prove the existence of a narrow stream of material, a so-called jet, emerging from the only gravitational wave event involving two neutron stars observed so far. With its high sensitivity and excellent performance, the 100-m radio telescope in Effelsberg played an important role in the observations.
In August 2017, two neutron stars were observed colliding, producing gravitational waves that were detected by the American LIGO and European Virgo detectors....
Up to now, OLEDs have been used exclusively as a novel lighting technology for use in luminaires and lamps. However, flexible organic technology can offer much more: as an active lighting surface, it can be combined with a wide variety of materials, not just to modify but to revolutionize the functionality and design of countless existing products. To exemplify this, the Fraunhofer FEP together with the company EMDE development of light GmbH will be presenting hybrid flexible OLEDs integrated into textile designs within the EU-funded project PI-SCALE for the first time at LOPEC (March 19-21, 2019 in Munich, Germany) as examples of some of the many possible applications.
The Fraunhofer FEP, a provider of research and development services in the field of organic electronics, has long been involved in the development of...
For the first time, an international team of scientists based in Regensburg, Germany, has recorded the orbitals of single molecules in different charge states in a novel type of microscopy. The research findings are published under the title “Mapping orbital changes upon electron transfer with tunneling microscopy on insulators” in the prestigious journal “Nature”.
The building blocks of matter surrounding us are atoms and molecules. The properties of that matter, however, are often not set by these building blocks...
Scientists at the University of Konstanz identify fierce competition between the human immune system and bacterial pathogens
Cell biologists from the University of Konstanz shed light on a recent evolutionary process in the human immune system and publish their findings in the...
Laser physicists have taken snapshots of carbon molecules C₆₀ showing how they transform in intense infrared light
When carbon molecules C₆₀ are exposed to an intense infrared light, they change their ball-like structure to a more elongated version. This has now been...
11.02.2019 | Event News
30.01.2019 | Event News
16.01.2019 | Event News
22.02.2019 | Physics and Astronomy
22.02.2019 | Materials Sciences
22.02.2019 | Life Sciences