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| Author(s): |
Naara Marcondes dos Santos
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI) |
| Defense date: | 2019-05-20 |
| Examining board members: |
Marilis do Valle Marques;
Regina Lúcia Baldini;
Andrea Balan Fernandes;
Cristina Elisa Alvarez Martinez
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| Advisor: | Marilis do Valle Marques |
| Abstract | |
Caulobacter crescentus is an oligotrophic α-proteobacterium that lives in aquatic environments and can colonize environments with little availability of nutrients constantly suffering from nutritional deficiency. TonB dependent transporters (TBDT) transport iron bound to siderophores through the outer membrane of Gram-negative bacteria. When C. crescentus is in iron deficiency, four TBDT are highly expressed, encoded by CCNA_00138, CCNA_00028, CCNA_03023, and CCNA_02277 (HutA). C. crescentus NA1000 presents in its genome two genes encoding TonB proteins (CCNA_02419 and CCNA_02412), which are the energizing components of the transport. This work aimed to elucidate which iron source is transported by each of these four receptors and the role of each of the TonB proteins. Amino acid sequence analyses of the TBDTs showed that these proteins present little conservation among them, unlike the TonB proteins that present high conservation. A structural analysis was carried out by modeling all studied proteins in order to characterize these proteins in C. crescentus, and it was possible to identify some conserved regions in the TBDTs, such as the TonB box and the plug. Mutant strains were constructed for the six C. crescentus genes encoding TBDT and TonB proteins. In the phenotypic analysis of these mutants, growth and viability assays were carried out in different iron sources, and only 00028 presented a different growth pattern when compared to the NA1000 wild type strain, and could have a role in transporting ferric ions. The tonB strains did not show any difference in growth with the iron sources tested, but growth assays in plates with different carbon sources, showed differences in growth between mutant and wild type strains, for some of the sources. Site-directed mutatgenesis in hutA we carried out substituting some residues for Cysteine, in order to verify which amino acids in the loops are important for siderophore recognition and transport. (AU) | |
| FAPESP's process: | 17/02127-9 - Characterization of iron transport systems in Caulobacter crescentus |
| Grantee: | Naara Marcondes dos Santos |
| Support Opportunities: | Scholarships in Brazil - Master |