Septins are members of a conserved group of GTP-binding and filament-forming proteins involved in cytokinesis and a variety of other important cellular processes. Although hetero-oligomeric complex have been extensive investigated, homo-oligomeric structures have also been observed, and characterized as amyloid filaments, involved in neurodegenerative diseases. In this study we propose a structural analysis of hetero and homofilaments composed of septins. Regarding the heterofilament, the complexes containig the septins SEPT9, SEPT6, SEPT7 and SEPT11, SEPT5, SEPT7 will be produced in E. coli and purified. Transmission Electron Microscopy and Cryomicroscopy will be used in the characterization of these heterofilaments. Associated with these techniques, single-particle analysis and 3D molecular reconstitucion will enable us to produce low resolution images of protein complexes. In relation to the homofilaments, regions in the primary structure of human septin 2 (SEPT2), predicted to be responsible for the assembly of amyloidogenic structures, will be synthesized. The amiloidogenic homofilaments will be also characterized using Transmission Electron Microscopy and Cryomicroscopy associated with single-particle analysis and 3D molecular reconstitucion. Also in the case of amyloid homofilaments, Nuclear Magnetic Resonance will be used as alternative to provide further structural information. Thus, the identification of new complexes of septins, as well as their structural organization, is expected to give insights providing a better understanding the function of these proteins. In addition, a better characterization of the amyloid homofilaments could contribute to the elucidation of the involvement of SEPT2 in neurodegerenativas disorders.
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