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
Bioenergy cropland expansion could be as bad for biodiversity as climate change
11.12.2018 | Senckenberg Forschungsinstitut und Naturmuseen
How glial cells develop in the brain from neural precursor cells
11.12.2018 | Universitätsmedizin der Johannes Gutenberg-Universität Mainz
Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...
What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.
Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...
Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.
Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...
New Project SNAPSTER: Novel luminescent materials by encapsulating phosphorescent metal clusters with organic liquid crystals
Nowadays energy conversion in lighting and optoelectronic devices requires the use of rare earth oxides.
Scientists have discovered the first synthetic material that becomes thicker - at the molecular level - as it is stretched.
Researchers led by Dr Devesh Mistry from the University of Leeds discovered a new non-porous material that has unique and inherent "auxetic" stretching...
10.12.2018 | Event News
06.12.2018 | Event News
03.12.2018 | Event News
11.12.2018 | Physics and Astronomy
11.12.2018 | Materials Sciences
11.12.2018 | Information Technology