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| Author(s): |
Janaina Areias Paulela
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI) |
| Defense date: | 2018-04-20 |
| Examining board members: |
Mário Henrique de Barros;
Felipe Santiago Chambergo Alcalde;
Marcio Vinícius Bertacine Dias;
Andrea Balan Fernandes;
Graziella Eliza Ronsein
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| Advisor: | Mário Henrique de Barros |
| Abstract | |
Coenzyme Q (CoQ) is a molecule of essential function in the transfer of electrons of the mitochondrial respiratory chain. In saccharomyces cerevisiae , CoQ is constituted by a benzene ring associated with a polyprenyl chain with 6 repetition units, being therefore also denominated CoQ6 or Q6. Thirteen nuclear genes have already been identified (COQ1 COQ11, ARH1 and YAH1) required for coenzyme Q biosynthesis. Most of Coq products are physically associated in a biosynthetic complex anchored at the mitochondrial internal membrane. In this project, we identified Coq3p and Coq7p residues relevant for their respective role in CoQ synthesis combining bioinformatics analyzes with phenotypic tests for functional mapping. Coq7p is a carboxylate-bridged di-iron protein that catalyzes the hydroxylation of demetoxy-Q6 (DMQ6), the last monooxygenase step in the synthesis of CoQ. In this study, we found a group of residues that modulate the activity and stability of Coq7p: D53, R57, V111 and S114. While R57, V111 and S114 are highly conserved residues, V111 and S114 are correlated in communities of coevolution. We also demonstrate that the double mutant S114A, V111G and the mutant S114E have respiratory deficiency at non-permissive temperature, in addition to accumulating of the intermediate DMQ6 and low amounts of Q6, thus concluding that phosmimetic S114E inhibits the activity of Coq7p. Hence, we propose that the phosphorylation of S114 is required to move a loop between helices 2 and 3, thus affecting the activity of the catalytic center Coq7p. For its part, Coq3p acts as a methyltransferase, catalyzing different steps during biosynthesis of CoQ. Here we identified residues that collaborate for functional activity of Coq3p: E123, S125, C131, G133, G134, H165, D203, E219, K258 and S262. Mutants E123A, H165A, D203A, E219A, K258A and S62A, have mild respiratory growth, and expression of Coq3p levels similar to the wild strain, in addition to accumulating low amounts of Q6. While C131, G133, and G134 are residues highly conserved, located in a loop in the space between beta sheets, the overexpression of the mutants C131A, G133A and G134A present respiratory growth in medium containing non-fermentable carbon source, in addition to accumulate Q6 compatible with the levels of protein expression. We propose a model for Coq3p, with residues C131, G133 and G134 as part of Coq3p catalytic center. (AU) | |
| FAPESP's process: | 12/11524-8 - Characterization of Saccharomyces cerevisiae strains and human fibroblast cultures defectives in the biosynthesis of coenzyme Q |
| Grantee: | Janaina Areias Paulela |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |