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| Author(s): |
Diego Antonio Leonardo Cabrejos
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2020-12-08 |
| Examining board members: |
Richard Charles Garratt;
Andre Luis Berteli Ambrosio;
Shaker Chuck Farah;
Marcos Roberto de Mattos Fontes;
Beatriz Gomes Guimarães
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| Advisor: | Richard Charles Garratt |
| Abstract | |
Septins are involved in several cellular processes (cytokinesis, spermatogenesis, apoptosis, etc.), which is why they are related to the development of several diseases. Belonging to the GTPase family, they present three domains: highly variable N and C terminal and a conserved G domain (binding to GTP/GDP). To perform their functions, one septin from each group (4 different groups in humans) associate to form heterofilaments using two types of interface: the G interface and the NC interface. Although the type of contact interface and the specific order of septins in the filament are known, the molecular mechanisms that control the correct polymerization of the filament are still unknown. Here, we describe studies carried out on the G and NC interfaces of septins, in order to shed light on the molecular mechanisms of specific interaction and to verify the replacement of septins by others from the same group. Eight combinations of septin “G” heterocomplexes were co-expressed and purified and characterized by biophysical techniques. They were present as homogeneous heterodimers in solution (SEC and SEC-MALS) with the presence of GTP and GDP in approximately equimolar proportions. In addition, each dimer exhibited a different thermal stability, which may indicate an interaction preference for complex formation. Crystallographic studies of the G heterodimers allowed for the identification of specific interactions that determine the specificity of the complex formed by septins from group II and group III (validating the replacement of septins from the same group) and helping to explain the presence of a catalytically inactive group in these proteins. On the other hand, the crystal structures of the coiled-coils of septins 1, 4 and 5 (NC interface) allowed us to observe a new protein motif that suggests that it is related to the interaction between two heterofilaments, forming highly complex structures of septins (networks etc.). (AU) | |
| FAPESP's process: | 16/04658-9 - Structural determinants for specific interaction of interfaces G and NC of septins: validating the substitution rules in the assembly of the filament |
| Grantee: | Diego Antonio Leonardo Cabrejos |
| Support Opportunities: | Scholarships in Brazil - Doctorate |