Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pinpointing Protein Locations

13.02.2013
An innovative technique which pinpoints protein locations and helps researchers unravel the protein's functions has been developed by the researchers from the Massachusetts Institute of Technology (MIT), researchers who recently moved from MIT to the Ulsan National Institute of Science (UNIST) explain.
Scientist from MIT have now developed a technique that can tag all of the proteins in a particular region of a cell, allowing them to more accurately map those proteins.

“There was no previous high-quality map of the matrix subdomain of mitochondria, and now we have one” said Alice Ting, the Ellen Swallow Richards Associate Professor of Chemistry at MIT. “We’re still really far from that goal, but the overarching motivation is to get closer to that goal.”

Diagram of a mitochondrion

This innovative technique combines the strengths of two existing techniques — microscopic imaging and mass spectrometry — to map proteins in a specific cell location and generate a comprehensive list of all the proteins in that area.

In a paper appearing in the Jan. 31 online edition of Science, Rhee and colleagues used the new technique to identify nearly 500 proteins located in the mitochondrial matrix — the innermost compartment found in mitochondria, which can be thought of as the power houses of the cell where energy is generated. Previous attempts to map the entire set of proteins in the matrix (proteome) yielded a list of only 37 proteins.

Protein labeling

Using fluorescence or electron microscopy, scientists can determine protein locations with high resolution, but only a handful of a cell’s ~20,000 proteins can be imaged at once. “It’s a bandwidth problem,” Ting says. “You certainly couldn’t image all the proteins in the proteome at once in a single cell, because there’s no way to spectrally separate that many channels of information.”

With mass spectrometry, which uses ionization to detect the mass and chemical structure of a compound, scientists can analyze a cell’s entire complement of proteins in a single experiment. However, the process requires dissolving the cell membrane to release a cell’s contents, which jumbles all of the proteins together. By purifying the mixture and extracting specific organelles, it is then possible to figure out which proteins were in those organelles, but the process is messy and often unreliable.
The new MIT approach tags proteins within living cells before mass spectrometry is done, allowing spatial information to be captured before the cell is broken apart. This information is then reconstructed during analysis by noting which proteins carry the location tag.

The new system makes use of a chemical tag that includes biotin, one of the B vitamins. To label proteins with biotin, the researchers first designed a new enzyme they dubbed APEX. This enzyme is a *peroxidase*, meaning that it removes an electron and a proton in a reaction known as oxidation.
“What you do is tag the proteins with biotin while the cell is still alive, and then you just pull out those proteins,” Ting says. “Therefore you bypass all of the problems that are associated with trying to purify regions of cells and organelles, because you don’t have to anymore.”

A comprehensive list

To demonstrate the technique’s power, the researchers created a comprehensive list of the proteins found in the mitochondrial matrix. Most of a cell’s energy generation takes place in mitochondria, as well as many biosynthetic processes.
Using the new method, the team increased the number of proteins known to be located in the mitochondrial matrix. “There was no previous high-quality map of the matrix subdomain of mitochondria, and now we have one,” says Ting, adding that this new wealth of information should help biologists to learn more about the functions of many of those proteins.

Already, the team has found that an enzyme called ppox — involved in synthesizing heme, the iron-porphyrin complex found in hemoglobin — is not located where biologists had thought it was. As heme precursors move through the biosynthetic pathway, they are shuttled to different parts of the cell. Finding that ppox is in the matrix means that there must be unknown transporter proteins bringing heme precursors into the matrix, Ting says.

The researchers are now investigating proteins found in another compartment of the mitochondria, the intermembrane space. They are also modifying the chemistry of the labeling system so they can use it for other tasks such as mapping the topology of membrane proteins and detecting specific protein-protein interactions.

The lead scientists of this research are Hyun-Woo Rhee (former MIT postdoc, currently Assistant Professor, School of Nano-Bioscience and Chemical Engineering, UNIST) and Peng Zou, who received a PhD from MIT in 2012.

REFERENCE:

Hyun-Woo Rhee, Peng Zou, Namrata D. Udeshi, Jeffrey D. Martell, Vamsi K. Mootha, Steven A. Carr, and Alice Y. Ting. 2013. Proteomic Mapping of Mitochondria in Living Cells via Spatially Restricted Enzymatic Tagging. Science 1230593. Published online 31 January 2013 [DOI:10.1126/science.1230593]
Journal information
ScienceXpress

Eunhee Song | Research asia research news
Further information:
http://www.unist.ac.kr
http://www.researchsea.com

More articles from Life Sciences:

nachricht CRISPR meets single-cell sequencing in new screening method
19.01.2017 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften

nachricht Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Global threat to primates concerns us all

19.01.2017 | Ecology, The Environment and Conservation

Scientist from Kiel University coordinates Million Euros Project in Inflammation Research

19.01.2017 | Awards Funding

The Great Unknown: Risk-Taking Behavior in Adolescents

19.01.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>