MFPL - 2016 RESEARCH GROUPS
KRISTINA DJINOVIĆ-CARUGO
Structural biology of the cytoskeleton Animal movement is mediated by striated muscles, with the sarcomere being the basal contractile unit within single muscle fibers. Sarcomeric actin and myosin form cross-linked and interdigitated filament bundles whose sliding motion generates force. Antiparallel actin filaments from adjacent sarcomers are anchored at the Z-disk, which plays a central role as the site organizing the molecular machinery that is required for muscle contraction and is regarded as one of the most complex assemblies known to biology (Figure 1A-C).
Kristina Djinović-Carugo
TEAM Oliviero Carugo Julian Ehrmann Irina Grishkovskaya Andreas Hagmüller Tamas Hatfaludi Stefan Hofbauer Julius Kostan Joan Lopez Arolas Moritz Madern Georg Mlynek Miriam Pedron Martin Gerald Puchinger Dominic Pühringer Sara Sajko Claudia Schreiner Julia Schweighofer Antonio Sponga Valeria Stefania Tobias Thöni Karolina Zielinska
We collaborate with several groups at MFPL (Warren, Slade, Skern, Kovarik, Blaesi, Moll), as well as with C. Obinger (University of Natural Resources and Life Sciences, Vienna) (Figure 2). Figure 1. Schematic representation of muscle, its filaments and of the Z-disk. (A) Muscle is composed of a bundle of fibers – muscle cells, which are in turn composed of myofibrils, the building unit of which is a sarcomere. (B) Sarcomere, with its major filaments actin, myosin and titin and the Z-disk anchoring cross linker α-actinin. (C) In the Z-disk actin and titin filaments are cross-linked by its major component α-actinin. (D) A surface representation of the alpha-actinin dimer (Ribeiro Ede et al., Cell, 2014) against a background of muscle sarcomeres viewed under the electron microscope. The sarcomeres display a typical striated pattern, and are connected via joint Z-discs, seen as dark black and grey diagonal stripes. Credit: Julius Kostan, Joan L. Arolas, Tobias Thoeni, Nikos Pinotsis, Kristina Djinović-Carugo, Uni Vienna; Mathias Gautel and Andrea Ghisleni, KCL; Marija Nabernik, Jernec Zupanc, Seyens
The major questions we are addressing are: What is the stoichiometry of the components and the assembly hierarchy of the Z-disk? What is the molecular architecture of both pre- and myofibrillar assemblies? Our long-term goal is to reconstitute a functional Z-disk from individual components, which is the best way to truly understand their disparate functional roles and molecular mechanisms. Apart from its major component α-actinin-2 (Ribeiro Ede et al., Cell, 2014) (Figure 1D), which accounts for ∼20% of the Z-disk mass, the current inventory of proteins in mature Z-disks includes over 40 proteins that form a highly stable and highly ordered unit that can support contractile forces of the muscle. The production of 16 Z-disk proteins is already well established in our laboratory. We use integrative structural biology approaches combining biochemical, biophysical and high resolution structural studies (X-ray diffraction, NMR) with lower resolution approaches that can either yield molecular envelopes (SAXS, SANS, EM) or specific distance information derived from e.g. chemical-cross-linking coupled to mass-spectrometry or NMR. New bioinformatic strategies are being designed to extend our prediction and analysis capabilities.
Figure 2. Examples of collaborative projects. (A) Crystal structure of heptameric SmAP2 from Sulfolobus solfataricus (Märtens et al., Life (Basel), 2015) (B) Overview showing the S2– S1 complex structure assembled from two protomers, with S1 in blue, S2 in yellow. Zn2+ is depicted as a green sphere (Byrgazov et al., Nucleic Acids Res., 2015). (C) Crystal structures of dimeric chlorite dismutase from Nitrobacter winogradskyi (Mlynek et al., J Bacteriol., 2011) and pentameric chlorite dismutase (Kostan et al., J Struct Biol., 2010). (D) Crystal structure of HemQ from Listeria monocytogenes catalyzing the decarboxylation of coproheme to heme b (accepted in FEBS Journal). Credit: Georg Mlynek, Irina Grishkovskaya, Kristina Djinović-Carugo, Uni Vienna
In order to overcome the major bottlenecks in structural and functional studies of proteins, which are availability of milligram amounts of active, chemically and conformationally pure protein and crystallization, an FFG funded Laura Bassi Centre for Optimized Structural Studies (COSS) was established as a joint venture of IMP, Biomin and UNIVIE-MFPL with the goal to set-up an efficient platform to combine the recent advances in protein production and develop customized crystallisation approaches.
SELECTED PUBLICATIONS Ribeiro Ede A Jr, Pinotsis N, Ghisleni A, Salmazo A, Konarev PV, Kostan J, Sjöblom B, Schreiner C, Polyansky AA, Gkougkoulia EA, Holt MR, Aachmann FL, Zagrović B, Bordignon E, Pirker KF, Svergun DI, Gautel M, Djinović-Carugo K. The structure and regulation of human muscle α-actinin. Cell. 2014 Dec 4;159(6):1447-60. PMID: 25433700 Song JG, Kostan J, Drepper F, Knapp B, de Almeida Ribeiro E Jr, Konarev PV, Grishkovskaya I, Wiche G, Gregor M, Svergun DI, Warscheid B, Djinović-Carugo K. Structural insights into Ca2+-calmodulin regulation of Plectin 1a-integrin β4 interaction in hemidesmosomes. Structure. 2015 Mar 3;23(3):558-70. PMID: 25703379 Kostan J, Salzer U, Orlova A, Törö I, Hodnik V, Senju Y, Zou J, Schreiner C, Steiner J, Meriläinen J, Nikki M, Virtanen I, Carugo O, Rappsilber J, Lappalainen P, Lehto VP, Anderluh G, Egelman EH, Djinović-Carugo K. Direct interaction of actin filaments with F-BAR protein pacsin2. EMBO Rep. 2014 Nov;15(11):1154-62. PMID: 25216944
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