Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Measuring modified protein structures

15.09.2014

Cells regulate protein functions in a wide variety of ways, including by modifying the protein structure. In an instant, a protein can take on another form and perform no or even the "wrong" function:

In humans, proteins that fold wrongly can cause serious diseases such as Alzheimer's, Parkinson's or cystic fibrosis. Some of these proteins also have a tendency to "infect" other molecules of the same type and congregate into insoluble so-called amyloid fibrils or plaques. These amyloids can damage cells and tissues and make people ill.

Method breaks the shackles

Until now, there has been a lack of methods that enable structurally modified proteins to be recorded quantitatively in complex biological samples. Although there is a series of techniques to study structurally modified proteins, such as x-ray crystallography, nuclear magnetic resonance spectroscopy and other spectroscopic techniques, they cannot be used to analyse complex biological samples.

Other procedures that researchers have used to study structural changes ofproteins in cells also have their limits: prior to the analysis, the proteins of interest have to be specifically marked to enable the scientists to observe them in samples. However, this approach is only possible for a few proteins in a sample.

The team headed by Paola Picotti, a professor of protein network biology, has now found a way to measure the majority of structurally modified proteins in any biological sample, which can contain thousands of different proteins. Picotti and her team have succeeded in measuring quantities of structurally modified proteins directly from a complex protein mixture as it occurs in cells, without cleaning or enriching the samples.

Combination of several methods

For their new method, the researchers combined an "old" technique and a modern approach from proteome research. First of all, familiar old digestive enzymes such as proteinase K are added to the sample, which cut the proteins depending on their structure into smaller pieces known as peptides.

The fragments can then be measured using a technique which Picotti played a key role in co-developing during her time as a postdoc at ETH Zurich (as ETH Life reported). Known as Selected Reaction Monitoring (SRM), this method enables many different peptides to be sought specifically and their quantities measured. Based on the peptides found, proteins that were originally present in the sample can be determined and quantified.

What makes it so special: the digestive enzymes cut the same kind of proteins that have different structures in different places, resulting in diverse fragments. Like a fingerprint, these fragments can be clearly assigned to the individual structures of the protein.

"This means we can use the method to analyse structural changes of specific proteins or entire protein networks in a targeted fashion and measure numerous proteins at the same time," says Picotti.

Works for protein responsible for Parkinson's

Based on their new method, the researchers devised a test to specifically measure the "healthy" and "sick" versions of the protein alpha-synuclein in complex, unpurified samples such as blood or cerebrospinal fluid. Alpha-synuclein is thought to cause Parkinson's when its structure is modified. The pathological structural variety congregates with its own kind to form amyloid fibrils, which harm neuronal cells.

With the aid of the test, the scientists managed to measure the exact amount of pathogenic and non-pathogenic alpha-synuclein directly in a complex sample. The test also yielded information on the structure of the protein. "It shows us which parts of the protein change and turn into the new pathological structure," says Picotti.

Increasing number of amyloidoses

For the time being, the concentration of alpha-synuclein cannot be used as a biomarker as the levels of the protein are too similar in the blood or cerebrospinal fluid of Parkinson's sufferers and healthy people. "Nevertheless, it is possible that the ratio of pathological versus nonpathogenic alpha-synuclein structure changes with time, along the progression of the disease" suspects the ETH-Zurich professor.

"As the new method enables us to measure both structures of the alpha-synuclein protein in a large variety of samples, it might be possible to use this to develop new biomarkers for this disease in the future," she hopes. Using the method, it might also be conceivable to discover other, as yet unknown amyloid-forming proteins that are connected to diseases without prior knowledge.

Both applications – the quantification of a specific known protein with a modified structure and the discovery of new proteins with variant structures – are highly relevant from a medicinal perspective, Picotti explains. "The number of amyloidoses, i.e. diseases that develop due to changes in protein structures, increases every year."

###

Feng Y, De Franceschi G, Kahraman A, Soste M, Melnik A, Boersema P, Polverino de Laureto P, Nikolaev Y, Oliveira AP, Picotti P. Global analysis of protein structural changes in complex proteomes. Nature Biotechnology, published online 14th Sept 2014, DOI: 10.1038/nbt.2999

Paola Picotti | Eurek Alert!
Further information:
http://www.ethz.ch/index_EN

Further reports about: ETH Measuring Parkinson's diseases fibrils fragments peptides proteins structure structures

More articles from Life Sciences:

nachricht Making fuel out of thick air
08.12.2017 | DOE/Argonne National Laboratory

nachricht ‘Spying’ on the hidden geometry of complex networks through machine intelligence
08.12.2017 | Technische Universität Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

Im Focus: A transistor of graphene nanoribbons

Transistors based on carbon nanostructures: what sounds like a futuristic dream could be reality in just a few years' time. An international research team working with Empa has now succeeded in producing nanotransistors from graphene ribbons that are only a few atoms wide, as reported in the current issue of the trade journal "Nature Communications."

Graphene ribbons that are only a few atoms wide, so-called graphene nanoribbons, have special electrical properties that make them promising candidates for the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

Blockchain is becoming more important in the energy market

05.12.2017 | Event News

 
Latest News

Making fuel out of thick air

08.12.2017 | Life Sciences

Rules for superconductivity mirrored in 'excitonic insulator'

08.12.2017 | Information Technology

Smartphone case offers blood glucose monitoring on the go

08.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>