SCIENTISTS GAIN UNIQUE INSIGHT INTO THE FUNCTION OF A KEY MUSCLE PROTEIN
Thanks to the first high-resolution structural analysis of the muscle protein α-actinin, scientists now have a better understanding of how muscles work.
The analysis provides crucial information about the structure and function of this complex muscle protein and could lead to the development of new treatments for major muscular disorders.
The results of the project, which is funded by the Austrian Science Fund FWF and the European Commission, were recently published in the prestigious scientific journal Cell.
Muscles move many things – but first and foremost themselves. Filaments of special proteins pull against each other so that the muscle can exert force. This only works if there is a fixed point, which anchors the filaments.
These locations are known as Z-disks and are largely composed of the protein α-actinin. An international research team headed by Kristina Djinovic-Carugo from the Max F. Perutz Laboratories of the University of Vienna and Medical University of Vienna has taken a closer look at this protein.
FUNCTION FOLLOWS FORM
"We not only succeeded in describing the exact structure of the protein for the first time", explains Djinovic-Carugo, "we were also able to confirm the long-held assumption about how its function is regulated."
It emerged from the structural research that showed that α-actinin exists as a dimer, a complex consisting of two identical molecules, and that it displays a cylindrical shape, 360 Å in length (1 Å = 10 to the power of -10 metres) and 60 Å wide. Each individual molecule of the dimer has a head-and a neck-like structure followed by a four-part rod-shaped extension.
Two protein domains protruding from the rod-shaped extension in an L-shaped formation proved to be particularly interesting. "These L-shaped domains connect to the neck of the other molecule and this interaction is important for function", describes Djinovic-Carugo. "However, the really exciting discovery about these domains arose when we added the fatty acid molecule PIP2."
Scientists had actually speculated for years that PIP2 plays a key role in the functioning of muscle α-actinin. This hypothesis remained unconfirmed, however, until the following observation was made during the study of Djinovic-Carugo and her international colleagues in Germany, United Kingdom, Norway, Russia, Switzerland and Slovenia: as long as there is no PIP2 available, the L-shaped domain remains connected to the neck of the second α-actinin.
If PIP2 is available, the connection opens and renders the domain available to bind to another muscle protein – titin. The trick here – as revealed by the structural data from this FWF project – is that the neck region of the α-actinin is similar in structure to titin.
If there is no PIP2, one of the L-shaped domain of an α-actinin molecule binds to a titin-lookalike region in the neck of the opposing molecule. If PIP2 is present, the L-shaped part detaches from the neck and binds titin. The presence of PIP2 is sufficient to change the binding parameters in such a way that the one is prioritised over the other.
X-RAY VIEW OF THE CRYSTAL BALL
Regarding the methodology used in the study, Djinovic-Carugo says: "To deduce the functioning of a protein from its structure, you have to be able to identify everything down to a billionth of a metre. This is only really possible using X-ray diffraction, in which X-ray beams diffract when they encounter the fine structures of a protein, which is presented in the form of a crystal."
However, the decision to use this technology involved a tough test of the scientists’ patience at the outset: it took years to produce sufficient amounts of α-actinin to grow the protein crystals. The clarification of how α-actinin is regulated by PIP2 necessitated the use of other complicated complementary analysis methods, and this is where the expertise of Djinovic-Carugo’s international colleagues was indispensable. The comprehensive findings, which were recently acknowledged through the publication of the study in Cell, show that the long and concerted effort was worthwhile.
The importance of the project’s results extends far beyond the basic insights they provide. α-Actinin plays a role in the causes of life-threatening muscular disorders like dystrophies and cardiomyopathies. The new insights into the structure and function of this protein could lead to the development of new approaches to their treatment.
Professor Kristina Djinovic-Carugo is an internationally renowned expert in the x-ray diffraction of proteins. She heads the Department of Structural and Computational Biology ( http://zmb.univie.ac.at/en/structure-of-the-zmb/department-of-structural-and-computational-biology/ ) of the Max F. Perutz Laboratories ( https://www.mfpl.ac.at ) of the University of Vienna as well as the Laura Bassi Center for Optimized Structural Studies.
For information on Djinovic-Carugo’s research group, see: http://www.mfpl.ac.at/djinovic
Original publication: E. d. A. Ribeiro, N Pinotsis, A Ghisleni, A Salmazo, P. V. Konarev, J. Kostan, B. Sjoeblom, C. Schreiner, A. A. Polyansky, E. A. Gkougkoulia, M. R. Holt, F. L. Aachmann, B. Žagrović, E. Bordignon, K. F. Pirker, D. I. Svergun, M. Gautel and K. Djinović-Carugo: The structure and regulation of human muscle α-actinin. Cell 158, 1447 – 1460, Dec. 04, 2014 DOI: http://dx.doi.org/10.1016/j.cell.2014.10.056
Link to the publication: http://www.cell.com/cell/abstract/S0092-8674(14)01428-7
Prof. Kristina Djinovic-Carugo
Max F. Perutz Laboratories University of Vienna Department of Structural and Computational Biology Campus Vienna Biocenter 5
1030 Vienna, Austria
M +43 / 664 / 602 77 522 03
Austrian Science Fund FWF:
Haus der Forschung
1090 Vienna, Austria
T +43 / 1 / 505 67 40 - 8111
Copy Editing & Distribution:
PR&D – Public Relations for Research & Education Mariannengasse 8
1090 Vienna, Austria
T +43 / 1 / 505 70 44
Marc Seumenicht | PR&D – Public Relations for Research & Education
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy