New findings help explain how molecules are speedily transported into and out of the cell's nucleus

New findings help explain how molecules are speedily transported into and out of the cell’s nucleus
Because it lacks a predictable structure, an FG Nup (green), a component of the nuclear pore complex, can interact quickly with a transport factor (purple) bound to large cargo. This interaction makes selective and rapid transport into and out of the nucleus possible.

A cell does everything it can to protect its nucleus, where precious genetic information is stored. That includes controlling the movement of molecules in and out using gateways called nuclear pore complexes (NPCs).

Now, researchers at The Rockefeller University, Albert Einstein College of Medicine, and the New York Structural Biology Center have identified the that makes both swift and cargo-specific passage through the NPC possible for large molecules.

Scientists are paying close attention to this regulation since dysfunction in nuclear transport has been linked to many diseases, including cancers and .

While small molecules can easily pass in and out of the nucleus, the transport of large molecules such as proteins and RNA is more complex and less well understood. These are moved through the NPC rapidly, but also selectively to avoid allowing the wrong big molecules through.

It was already known that proteins called bind to large cargo and escort it through the NPC. A team led by Michael P. Rout, a professor at Rockefeller University and head of the Laboratory of Cellular and Structural Biology, and David Cowburn, a professor of biochemistry and of physiology & biophysics at Albert Einstein College of Medicine, sought to explain the speed with which transport factors ferry large molecules across the NPC, a process that lasts only a few milliseconds.

"It's understood how these transport factors selectively choose and bind to their cargo," Rout says. "However, it's been unclear how such a specific process can also shepherd molecules through the nuclear pore complex so quickly."

At the center of the NPC, the transport factors and their cargo must pass through a selectivity filter made of proteins called FG Nups. These proteins form a dense mesh that normally prevents large molecules from getting through. Using a technique known as nuclear magnetic resonance spectroscopy, the researchers collected atomic-scale information about the behavior of the FG Nups, focusing on Nsp1, the most studied representative of the FG Nups.

Normally, proteins fold into large structures. Relative to small such as water, these large structures move very slowly. This means their interactions are correspondingly slow.

The researchers measured the physical state of FG repeats with and without transcription factors bound to them. They found that rather than folding like proteins generally do, the FG Nups are loose and string-like, remaining highly dynamic and lacking a predictable structure.

"Usually, binding between traditionally folded proteins is a time consuming, cumbersome process, but because the FG Nups are unfolded, they are moving very quickly, very much like . This means their interaction is very quick," explains Rout.

The disordered structure of the FG regions is critical to the speed of transport, allowing for quick loading and unloading of cargo-carrying transport factors. At the same time, because transport factors have multiple binding sites for FG Nups, they are the only proteins that can specifically interact with them—making transport both fast and specific.

"We observed that there is minimal creation of a static well-ordered structure in complexes of FG Nups and transport factors," says Cowburn. "Our observations are, we propose, the first case where the 'fuzzy' property of an interaction is a key part of its actual biological function."

The team hopes this discovery will lead to detailed characterizations of nuclear transport pathways and to more close studies of the NPC's function. Ultimately, a better understanding of how the NPC works will not only provide new insight into the basic biology of cells, but also have implications for health and disease.


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More information: "The molecular mechanism of nuclear transport revealed by atomic scale measurements." eLife, DOI: dx.doi.org/10.7554/eLife.10027
Journal information: eLife

Citation: New findings help explain how molecules are speedily transported into and out of the cell's nucleus (2015, September 18) retrieved 21 August 2019 from https://phys.org/news/2015-09-molecules-speedily-cell-nucleus.html
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Sep 18, 2015
Notice that no one here in this article even dares to make mention of the words "evolve" or "evolution".
With terms and phrases like transport, protection, cargo specific, nuclear pores, "regulation since dysfunction in nuclear transport has been linked to many diseases", slow and big when folded, small and fast when not, and so on, one has to question how life could have originated via random chemical and physical processes all by itself.
These terms and phrases clearly spell out predetermined, i.e. programmed action, shape and functionality. It could not have arisen by chance at all. Given the complexity involved no one would believe that a modern motor vehicle can arise by random actions, so only a true fool would believe such a thing as a cell springing into life from dead materials all by itself.

Sep 18, 2015
Who claims that a cell with a nucleus sprung into life by itself? A cell with a nucleus is a very complex life form that took several billion years to evolve from the complex chemistry / simply biology start of 'life'.

The modern vehicle is a good analogy - a modern motor vehicle didn't spring up from nothing - it evolved from simpler vehicles with fewer bells and whistles, which arose from adding a motor to a horse-drawn carriage, which evolved from a wagon whose wheels evolved from log rollers, etc., so a modern motor vehicle is a great example of evolution in action.

And don't underestimate natural selection acting on random events, only a tiny fraction of which are beneficial, and then copying the result. For example, an early step in that long chain that lead to a modern motor vehicle could easily have been seeing a round rock or log roll down hill by chance.


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