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| Author(s): |
Rafael Marques da Silva
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2022-04-26 |
| Examining board members: |
Richard Charles Garratt;
Heloisa Sobreiro Selistre de Araújo;
Júlio César Borges
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| Advisor: | Richard Charles Garratt |
| Abstract | |
Septins are structural proteins that normally present GTPase activity, playing an important role in the cell structure and acting as a scaffold in the recruitment of partner proteins. These proteins can be found in the most different living beings, such as protozoan, fungi and animals. In order to do so, different septins organize into heterofilaments that are stabilised by interactions between subunits that show two types of interface, known as G and NC interfaces. In yeast, four proteins are arranged into a linear filament that forms an octamer, which order is Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11. This octamer can then polymerize by its extremities, giving birth to more complex and longer filaments. Understanding the exact molecular mechanisms that control the correct polymerization of the individual filaments and their later packing into high order structures is one of the biggest challenges in the area of septins\' biochemistry. From the four previous yeast septins cited above, only Cdc11 was crystallized and had a crystal structure reported 1. However, the data related to this structure shows very poor quality, where serious problems concerning the stereochemical, crystallographic and statistical parameters of this crystal structure can be seen. For this reason, this work sought to re-determine the structure of Cdc11 using the protocol already described in the literature and, subsequently, to extend the structural studies to the other yeast septins. This work also aimed to analyze the biophysical properties of these four septins, such as oligomeric state in solution, thermal stability, their capacity to bind guanine nucleotides and hydrolyse GTP. It could be seen that Cdc3 and Cdc11, when expressed without their septin partner, are monomers in solution and are purified with no bound nucleotides, different than what could be verified concerning Cdc12, which is bound to both GDP and GTP due to its catalytic activity. The co-expression of Cdc3/Cdc10 and Cdc11/Cdc12 resulted in dimers that allowed the purification of Cdc12 and Cdc10 by SEC. Protein crystals were obtained for the septins Cdc11 and the complexes Cdc3/Cdc10 and Cdc11/Cdc12 that unfortunately diffracted at low resolution (4 5 Å), not resulting in a crystallographic structure. In view of the poor validation parameters of the crystallographic structure of Cdc11, models for this protein were generated as monomers and dimers, showing two different interfaces (G and NC) with different partners (Cdc12 and Cdc11), which are preferable than the crystallographic structure of Cdc11. (AU) | |
| FAPESP's process: | 18/09687-2 - Structural characterization of the yeast (Saccharomyces cerevisiae) septins Cdc3, Cdc10, Cdc11 e Cdc12 |
| Grantee: | Rafael Marques da Silva |
| Support Opportunities: | Scholarships in Brazil - Master |