So understanding what protein complexes look like and how they operate is the key to figuring out what makes cells tick. By harnessing the unique properties of polarized light, Rockefeller scientists have now developed a new technique that can help deduce the orientation of specific proteins within the cell.
By turning their instruments toward the nuclear pore complex, a huge cluster of proteins that serves as a gateway to a cell's nucleus, the scientists say they have filled in the gaps left by other techniques and made important new discoveries about how the complex works.
"Our new technique allows us to measure how components of large protein complexes are arranged in relation to one another," says Sandy Simon, head of the Laboratory of Cellular Biophysics. "This has the potential to give us important new information about how the nuclear pore complex functions, but we believe it can also be applied to other multi-protein complexes such as those involved in DNA transcription, protein synthesis or viral replication."
Although researchers have spent years studying the workings of the nuclear pore complex, there is still much that has remained mysterious. One problem is that there is a "resolution gap" between the two techniques primarily used to visualize protein complexes. Electron microscopy can reveal the broad outlines of a large protein complex, but it can't show details. X-ray crystallography, meanwhile, can show minute detail but only of a small piece of the complex; it can't say how the individual pieces fit together. To further complicate matters, both techniques require fixed samples – while they can give you an idea of what something looks like at a moment in time, they can't tell you how its pieces might move.
The new technique was developed by Simon along with postdoc Alexa Mattheyses, graduate student Claire Atkinson and Martin Kampmann, a former a member of Günter Blobel's Laboratory of Cell Biology who is currently at the University of California, San Francisco. It takes advantage of the properties of polarized light to show how specific proteins are aligned in relation to one another. After genetically attaching fluorescent markers to individual components of the nuclear pore complex, the scientists replaced the cell's own copy of the gene that encodes the protein with the new form that has the fluorescent tag. Then, they used customized microscopes to measure the orientation of the waves of light the fluorescently tagged proteins emitted. By combining these measurements with known data about the structure of the complex, the scientists can confirm or deny the accuracy of previously suggested models.
"Our experimental approach to the structure is synergistic with other studies being conducted at Rockefeller, including analysis with X-ray crystallography in Günter's lab and electron microscopy and computer analysis in Mike Rout's lab," says Simon. "By utilizing multiple techniques, we are able to get a more precise picture of these complexes than has ever been possible before."
The scientists used the technique to study nuclear pore complexes in both budding yeast and human cells. In the case of the human cells, their new data shows that multiple copies of a key building block of the nuclear pore complex, the Y-shaped subcomplex, are arranged head-to-tail, rather than like fence posts, confirming a model proposed by Blobel in 2007.
"As a graduate student with Günter Blobel, I determined the three-dimensional structure of the Y-shaped subcomplex using electron microscopy," says Kampmann. "However, it was still a mystery how these 'Y's are arranged. The new technique we have developed reveals the orientation of building blocks in the cell, and we hope that it will eventually enable us to assemble individual crystal structures into a high-resolution map of the entire nuclear pore complex."
Eventually, the scientists say their technique could go even further. Because the proteins' fluorescence can be measured while the cells are still alive, it could give scientists new insights into how protein complexes react to varying environmental conditions, and how their configurations change over time.
"What happens when other proteins pass through the nuclear pore? Does the orientation of the nucleoporins change? With this technique, can find out not only what the pore looks like when it's sitting still, but what happens to it when it's active," Simon says. Their first characterization of the dynamics of the nuclear pore proteins was published recently in The Biophysical Journal.
Zach Veilleux | EurekAlert!
20.11.2017 | Washington University in St. Louis
Carefully crafted light pulses control neuron activity
20.11.2017 | University of Illinois at Urbana-Champaign
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
20.11.2017 | Life Sciences
20.11.2017 | Trade Fair News
20.11.2017 | Earth Sciences