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.
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.
Prof. Doron Rapaport, PhD
University of Tübingen
Interfaculty Institute of Biochemistry
Phone +49 7071 29-74184
Dr. Kai Stefan Dimmer
University of Tübingen
Interfaculty Institute of Biochemistry (IFIB)
Phone +49 7071 29-74174
Dr. Karl Guido Rijkhoek | idw - Informationsdienst Wissenschaft
Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München
Second research flight into zero gravity
21.10.2016 | Universität Zürich
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences