In an Early Edition publication of The Proceedings of the National Academy of Sciences (PNAS) this week, the researchers demonstrate the "alpha-synuclein dance" – the switching back and forth of the protein between a bent helix and an extended helix as the surface that it is binding to changes.
Such shape shifting has rarely been so directly observed in proteins like alpha-synuclein, which are known to be unfolded in isolation, says the study's senior investigator Ashok Deniz, an associate professor at The Scripps Research Institute.
"We are intrigued to see such complex behavior," he says. "It is interesting that with just a single binding partner, the protein can undergo so many dramatic shape transitions, and that the whole process is reversible."
In the past, scientists believed that proteins, as directed by their genes, fold themselves into defined three-dimensional structures that dictate their function. But more recently, a class of proteins known as "intrinsically disordered proteins" have been identified, which are functional, despite the fact that they are often unfolded.
Alpha-synuclein is such a protein. Mutations in the gene that produces alpha-synuclein have been linked to early-onset Parkinson's disease, and in sporadic, common Parkinson's disease, the protein can accumulate into so-called Lewy bodies inside nerve cells. The protein is also found in the amyloid plaques in Alzheimer's disease, and in other forms of neurological disease.
To learn more about alpha-synuclein, the Scripps Research team decided to study the shape of single proteins. To do this, they used a technique they helped develop, which is known as single-molecule fluorescence resonance energy transfer (FRET), to look at how the protein folds when it binds to different molecules. This technique, which Deniz calls a "molecular ruler," measures light emitted from fluorescent dyes that are attached to amino acids in the protein. The measured light provides information about molecular distances, hence revealing the protein's shape. By observing shapes of individual proteins rather than averaging data over a large number of them, the team was able to better map and resolve shape complexity in the system.
To coax the protein to change shapes, the researchers increased the concentration of a soapy solution that mimics the lipids found in different nerve cell membranes in the brain. Alpha-synuclein is known to bind to membranes on nerve cells, and lipids are a large component of those membranes.
At a low concentration, the "lipid" molecules remained separate but at higher concentration, small and then larger blobs of molecules form. The shape of the alpha-synuclein kept pace – the extended helix could latch onto lipid-mimics as monomers or in a large cylinder-shaped blob, whereas the bent helix wrapped itself around smaller lipid-mimic balls or could create formations with lipid-mimic monomers.
"Others have found the protein to be in a bent helix or in an extended helix, but what we are showing here directly is that the shape can actively change," Deniz says. "It starts off in an unfolded state, and as we increase the concentration of the lipid mimics, the protein reacts to what is in effect a different binding partner, even though it is the same small molecule at different concentrations. It switches back and forth into different states.
"This is perhaps the most complex protein folding-binding system that has been studied to date using single-molecule FRET," he says.
This ability of alpha-synuclein to be switched into alternative shapes could play a significant role in regulating formation of disease-related aggregates, as well as enabling its function. Hence, one next step for the research team is to figure out which form of alpha-synuclein may accelerate formation of the types of protein aggregates found in Alzheimer's disease plaque and in Parkinson's disease Lewy bodies. Using single-molecule methods to directly construct binding-folding maps (as in the current work) will be a critical component of this future effort, and also should be widely applicable to other intrinsically disordered or amyloid-forming proteins.
Co-authors of the paper, "Interplay of á-synuclein binding and conformational switching probed by single molecule fluorescence," include first authors Allan Chris M. Ferreon and Yann Gambin, and Edward A. Lemke – all of The Scripps Research Institute.
This work was supported by a grant from the National Institute of General Medical Sciences, National Institutes of Health (NIH), and postdoctoral fellowships from the NIH National Institute of Neurological Disorders and Stroke, the La Jolla Interfaces in Science (funded by the Burroughs Wellcome Fund), and the Alexander von Humboldt Foundation.
About The Scripps Research Institute
The Scripps Research Institute is one of the world's largest independent, non-profit biomedical research organizations, at the forefront of basic biomedical science that seeks to comprehend the most fundamental processes of life. Scripps Research is internationally recognized for its discoveries in immunology, molecular and cellular biology, chemistry, neurosciences, autoimmune, cardiovascular, and infectious diseases, and synthetic vaccine development. Established in its current configuration in 1961, it employs approximately 3,000 scientists, postdoctoral fellows, scientific and other technicians, doctoral degree graduate students, and administrative and technical support personnel. Scripps Research is headquartered in La Jolla, California. It also includes Scripps Florida, whose researchers focus on basic biomedical science, drug discovery, and technology development.
Keith McKeown | EurekAlert!
Further reports about: > Alpha-Synuclein > Alzheimer > FRET > NIH > Parkinson > Science TV > alpha-synuclein dance > amino acid > amyloid plaques > bent helix > cell membrane > extended helix > intrinsically disordered proteins > lipid-mimic balls > nerve cells > neurological disease > single-molecule fluorescence resonance energy transfer > three-dimensional structures
Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München
Second research flight into zero gravity
21.10.2016 | Universität Zürich
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences