A bit mysteriously, some proteins manage to multitask even with structures that are unfolded and floppy—“intrinsically disordered.” In this week’s issue of Nature, scientists at The Scripps Research Institute (TSRI) report their discovery of an important trick that a well-known intrinsically disordered protein (IDP) uses to expand and control its functionality.
Links to Disease
E1A is worth studying not just because it facilitates adenovirus infections, but also because it’s a prime example of an IDP. Such proteins frequently play outsized roles in cells, as crucial “molecular hubs” within very large protein-interaction networks. IDPs also include proteins that are linked to major diseases, including the tumor suppressor protein p53, the alpha synuclein protein of Parkinson’s disease, and the amyloid beta and tau proteins of Alzheimer’s disease.
The simple, flexible structures of IDPs are often promiscuously “sticky,” which in principle explains why they would have multiple molecular partners. But IDPs don’t connect willy-nilly with other proteins, and scientists have wondered how they regulate their diverse interactions.
Wright’s laboratory and others have been studying these interactions using a technique called nuclear magnetic resonance (NMR) spectroscopy. However, E1A’s intrinsic stickiness means that it tends to aggregate at NMR-friendly concentrations, rendering this method of analysis problematic. (Most proteins, by folding up into complex shapes, effectively cloak their stickier bits.)
A Sensitive Technique
For the new study, Wright and his colleagues turned to Deniz, whose laboratory specializes in the use of sensitive, cutting-edge techniques to study the dynamics of disordered proteins and other biological molecules. One of these techniques, a quantum optics method known as single-molecule FRET, uses a tiny fluorescent beacon system to register distances between selected parts of a protein. In effect, this allows investigators to monitor in real time the shape-changes of E1A—characterized by Wright’s laboratory in earlier work—which mark its rapid couplings and uncouplings with other proteins.
“The technique is sensitive enough that we can use it at extremely low protein concentrations, even focusing on single E1A proteins to avoid the loss of information that comes from the usual averaging of results over multiple proteins,” Deniz said.
Postdoctoral fellows Allan Chris M. Ferreon and Josephine C. Ferreon, in the Deniz and Wright laboratories, respectively, used the single-molecule FRET method to detail the strengths (“affinities”) with which E1A binds to two of its most important protein partners. By mapping how these binding affinities change under different conditions, they were able to obtain key insights into how E1A manages its multiple interactions.
First, like many folded proteins, E1A turns out to employ a basic regulatory mechanism called allostery: when one protein partner binds at one part of the E1A structure, it changes the ability of the other major binding site on E1A to bind other partners.
For most proteins that use allostery, this change makes partner-binding at the other site more likely (“positive cooperativity”). For a minority, it makes partner-binding at the other site less likely (“negative cooperativity”). But E1A turns out to have the capacity for either positive cooperativity or negative cooperativity between its two major binding regions—depending on whether a third part of the protein is occupied. “Allostery itself is a mechanism for modulating a protein’s functions, and here we show that E1A takes it to another level by modulating allostery—modulating the modulation, in effect,” said Josephine Ferreon.
The finding helps explain how E1A generates and manages its functional complexity—a complexity that for viral proteins seems particularly necessary, considering how tiny viral genomes are in comparison to those of their animal hosts. Moreover, some of E1A’s key binding partners in infected cells are themselves hub-type IDPs. “So now you multiply the complexity—and you can see how proteins such as E1A manage to achieve so much so quickly within a cell,” said Allan Ferreon.
Wright regards the study as the start of a rewarding line of investigation using sensitive techniques such as single-molecule FRET. “The fact that we can get around the usual technical obstacles relating to IDPs and do these single-molecule experiments really opens up the study of IDP hub interactions,” he said.
Deniz concludes, “We’re definitely going to be studying more of these hub proteins, and I think we’re going to discover other fundamental principles by which they achieve complex layers of biological regulation and function.”
The study, “Modulation of allostery by protein intrinsic disorder” was funded by the National Institutes of Health (grants GM066833 and CA96865) and by the Skaggs Institute for Chemical Biology at TSRI.
About The Scripps Research Institute
The Scripps Research Institute (TSRI) is one of the world's largest independent, not-for-profit organizations focusing on research in the biomedical sciences. TSRI is internationally recognized for its contributions to science and health, including its role in laying the foundation for new treatments for cancer, rheumatoid arthritis, hemophilia, and other diseases. An institution that evolved from the Scripps Metabolic Clinic founded by philanthropist Ellen Browning Scripps in 1924, the institute now employs about 3,000 people on its campuses in La Jolla, CA, and Jupiter, FL, where its renowned scientists—including three Nobel laureates—work toward their next discoveries. The institute's graduate program, which awards PhD degrees in biology and chemistry, ranks among the top ten of its kind in the nation. For more information, see www.scripps.edu.
Mika Ono | Newswise
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences