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Non-canonical septins interactions: analysis of the interaction via G interface of SEPT3 and group II septins

Grant number: 14/11772-7
Support type:Scholarships in Brazil - Master
Effective date (Start): August 01, 2014
Effective date (End): July 31, 2016
Field of knowledge:Biological Sciences - Biochemistry
Cooperation agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
Principal Investigator:Richard Charles Garratt
Grantee:Paola Lanzoni
Home Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

Septins are filamentous proteins that bind to GDP-GTP and are present in the cytoskeleton of eukaryotic cells. This protein group was initially identified as participants of the cell division cycle in yeast (Hartwell, 1972), but was after identified in more complex organisms like plathelmints, higher animals, insects and more recently in algae. The number of expressed septins varies between organisms and for humans this number is 13 proteins which are divided into 4 groups according to their nucleotide sequence similarity. In humans, these proteins are related to several kinds of diseases like cancer, degenerative diseases and male infertility. The first structural studies were performed by Sirajuddin and colleagues (2007) when they could derive the crystal structure of a human septin filament composed by SEPT2 (group III), SEPT6 (group II) and SEPT7 (group IV). This trimer had been identified earlier by Kinoshita in immunoprecipitation assays in HeLa cells (Kinoshita et al, 2002). Based on the protein's homology of septins and on the physiological filament structure found, Kinoshita suggested rules for the canonical assembly of septin filaments, where a trimer is should be composed based on the SEPT2/6/7 filament where SEPT2 and SEPT6 could be replaced by another septin from the same group while SEPT7 could not be replaced by any other and therefore it is fundamental for filament formation. The validity of this rule were verified in double- and triple-hybrid experiments where different trimmers respecting the same rules were detected. However, further than these, it was also characterized septins interactions not suggested by Kinoshita (herein called non-canonical). Some non-canonical interactions are formed by group I septins interacting with group II septins via G interface, what lead to the proposal that group I septins would replace group III (SEPT2) in the filament described by Sirajuddin et al. The goal of this master's project is to describe biophysically and structurally the interactions between group I and group II septins by its G interface and contribute to clarify if there is a possibility that SEPT3, a group I septin, would replace SEPT2 in canonical filaments, broadening the knowledge about septins assembly. (AU)

Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
PAOLA LANZONI. Non-canonical septins interactions: analysis of the interaction via G interface of SEPT3 and group II septins. 2017. Master's Dissertation - Universidade de São Paulo (USP). Instituto de Física de São Carlos São Carlos.

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