HDAC · Structural studies on protein recognition and regulation

Structural studies on protein recognition and regulation

Project objectives This project deals with structural biology of protein-protein interactions and regulation. The focus was on two different systems; (i) histone deacetylases, which are important regulators of chromatin and cytoskeleton dynamic, and (ii) the actin cytoskeleton of the malaria parasite, Plasmodium. The main results of the project concern the latter topic. With the granted funding, the applicant was able to start up an independent research career at the Department of Biochemistry, University of Oulu, Finland. During the two-year funding period, also additional external funding was gained, enabling the group to expand. At the moment, the research group in Oulu is composed of one PhD student and two post-doctoral fellows. In addition, the principal investigator now has research activities and an Assistant Professorship at the Centre for Structural Systems Biology, Helmholtz Centre for Infection Research and University of Hamburg at the DESY synchrotron campus in Hamburg, Germany. There, the group is composed of one post-doctoral scientist, three PhD students, and a lab technician. The European Commission Marie Curie European Reintegration Grant funding was pivotal for getting the research project going, in order to be able to get more research funding for continuing and hiring additional group members for the project. We have determined high-resolution crystal structures of Plasmodium falciparum profilin alone and in complex with an octa-proline peptide (Kursula et al. 2008) and the two Plasmodium actin depolymerisation factors (Huttu et al. 2010, Singh et al. 2011). In addition, we have characterised the biochemical properties of the previously uncharacterised ADF2 (actin depolymerising factor 2), allowing for a detailed structure-function comparison between these two ADF isoforms, which seem to perform somewhat different functions in the malaria parasite. Our P. falciparum profilin structure is the first of an apicomplexan profilin and reveals fascinating new features, not seen in profilins from other species. These differences may reflect its binding properties to actin and, thus, the peculiar dynamical properties of the apicomplexan actin filaments, and our structure now serves as a starting point for further studies. We are especially interested in the binding mode of Plasmodium profilin to actin and to physiological proline-rich ligand proteins, such as formins. To this end, we have produced Plasmodium formin 1 and 2 FH1-FH2 domains, which we have shown by SAXS (Small-angle X-ray scattering) to be a dimer in solution, the shape of which resembles the mammalian formin mDia dimer. We have also shown that formin 1 does not bind to profilin but is an efficient nucleator of actin filaments, increasing the rate of polymerisation. On the contrary, peptides derived from Plasmodium formin 2 bind to profilin with a fairly high affinity compared to other profilin - proline-rich peptide complexes. This work is currently being finalised into a manuscript (Ignatev et al.). In the future, we are also aiming to determine crystal and SAXS structures of actin-formin-profilin complexes. The malaria parasite uses these cytoskeletal complexes, which are now the main focus of our studies, for both motility and invasion of their host cells. Once these mechanisms are understood at the molecular (or atomic) level, we hope to be able to look for ways to interfere with the processes of motility and invasion of this parasite responsible for the most devastating world-wide infectious disease. More information on the project can be found from the following websites http://www.biochem.oulu.fi/tutkimus/ikursula/ http://www.desy.de/~inari/ References Huttu J, Singh B, Bhargav SP, Sattler J, Schüler H and Kursula I (2010) Acta Cryst. F, 66: 583-587. Ignatev A, Bhargav SP, Kursula P and Kursula I (2011) In preparation. Kursula I, Kursula P, Ganter M, Panjikar S, Matuschewski K and Schüler H (2008) Structure 16: 1638-1648. Singh B, Sattler J, Chatterjee M, Huttu J, Schüler H and Kursula I (2011) J. Biol. Chem. 286: 28256-28264.

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