Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Pinpointing Protein Locations

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.


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

Eunhee Song | Research asia research news
Further information:

More articles from Life Sciences:

nachricht North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich

nachricht Researchers Discover New Anti-Cancer Protein
22.03.2018 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Custom sequences for polymers using visible light

22.03.2018 | Materials Sciences

Scientists develop tiny tooth-mounted sensors that can track what you eat

22.03.2018 | Health and Medicine

Mat baits, hooks and destroys pollutants in water

22.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>