Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Newly-discovered signal in the cell sets protein pathways to mitochondria

27.06.2016

Tübingen researchers investigate the complex makeup of vital cell organelles

Mitochondria are often described as the powerhouse in the cells of humans, plants and animals; but they also fulfill a number of other vital functions. These “organs” within the cell have an interesting past: They arose more than a billion years ago as a bacterium, which was adopted into a primeval cell.

In the course of evolution, nearly all the genes of the original bacterium have become part of the cell nucleus. One result of this is that most of the protein building-blocks in mitochondria are produced in the cell plasma and put in place via complex importation processes.

In two new studies, researchers at the University of Tübingen’s Interfaculty Institute of Biochemistry headed by Professor Doron Rapaport have shed light on the many questions raised by the construction of mitochondria organelles. Monika Sinzel und Dr. Kai Stefan Dimmer have discovered a new protein which is incorporated into the mitochondrial outer membrane.

Interestingly, enzymes in the inner membrane play the deciding role in the protein’s correct positioning. In the second study, Rapaport and another member of his working group, Tobias Jores, worked with colleagues from Frankfurt and Kyoto to discover more about the signal which transports beta-barrel proteins through the cell plasma and into place in the mitochondria. Scientists have been wondering for years what the signal looks like.

Depending on its type, a cell has anything from a mere handful to hundreds of mitochondria. Apart from generating energy, mitochondria play a role in the production of cell building blocks such as amino acids, nucleotides, and iron-sulfur clusters.

“Today we know that they are also key players in the cell signalling network. This role gives mitochondria a special significance in processes such as aging and programmed cellular death,” says Rapaport. Defects in the mitochondria can lead to a wide variety of muscular, metabolic, and neurodegenerative diseases. The organelles also have an effect in conditions such as diabetes, deafness, blindness, cancer, premature aging, dementia, and bacterial infections.

“Importing proteins from the plasma and into the right subsection of the mitochondria is an essential process for cell viability,” Rapaport explains. Scientists already knew about the signals which directed most of the mitochondrial proteins, he adds.

“But that was not true of the important group of beta-barrel proteins, which are incorporated into the outer mitochondrial membrane.” Rapaport and Jores uncovered the signal using biochemical experiments, structural analyses, and gene manipulation on yeast cells: One special protein element, the beta-hairpin, guides the beta-barrel proteins safely to the mitochondria.

The Tübingen researchers also identified a receptor on the mitochondrial surface which recognized the beta-hairpin signal. The Kyoto researchers worked out the structural aspects of this molecular interaction. “Our research partners in Frankfurt showed that it was the beta-hairpin signal and no other which determines the path of beta-barrel proteins. They put it onto proteins which were actually meant for the chloroplasts – the cell photosynthesis organs – but the proteins were nevertheless delivered to the mitochondria,” Rapaport says.

Publications:
Monika Sinzel, Tao Tan, Philipp Wendling, Hubert Kalbacher, Cagakan Özbalci, Xenia Chelius, Benedikt Westermann, Britta Brügger, Doron Rapaport & Kai Stefan Dimmer: Mcp3 is a novel mitochondrial outer membrane protein that follows a unique IMP-dependent biogenesis pathway. EMBO Reports, DOI 10.15252/embr.201541273.

Jores, T., A. Klinger, L. Groß, S. Kawano, N. Flinner, E. Duchardt-Ferner, J. Wöhnert, H. Kalbacher, T. Endo, E. Schleiff, and D. Rapaport (2016): Characterization of the targeting signal in mitochondrial β-barrel proteins. Nature Communications, in press.

Contact:
Prof. Doron Rapaport, PhD
University of Tübingen
Interfaculty Institute of Biochemistry
Phone +49 7071 29-74184
doron.rapaport[at]uni-tuebingen.de

Dr. Kai Stefan Dimmer
University of Tübingen
Interfaculty Institute of Biochemistry (IFIB)
Phone +49 7071 29-74174
kai-stefan.dimmer[at]uni-tuebingen.de

Dr. Karl Guido Rijkhoek | idw - Informationsdienst Wissenschaft
Further information:
http://www.uni-tuebingen.de/

More articles from Life Sciences:

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

nachricht The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>