Respiratory-induced coenzyme Q biosynthesis is regulated by a phosphorylation cycle of Cat5p/Coq7p
Résumé
Coenzyme Q6 biosynthesis in yeast is a well regulated process that requires the final conversion of the late intermediate demethoxy-Q6 (DMQ6) to Q6 in order to support respiratory metabolism in yeast. The gene CAT5/COQ7 encodes the Cat5/Coq7 protein that catalyzes the hydroxylation step of DMQ6 conversion to Q6. In this study, we demonstrated that yeast Coq7 recombinant protein purified in bacteria can be phosporylated in vitro using commercial PKA or PKC kinases in S20, S28 and T32 predicted phospho-amino acids. The total absence of phosphorylation in a Coq7p version containing alanine instead of these phospho-amino acids, the high extent of phosphorylation produced and the saturated conditions maintained in the phosphorylation assay indicate that probably no other putative amino acids are phosphorylated in Coq7p. In vitro assays have been corroborated in a phosphorylation assay performed in purified mitochondria without external or commercial kinases. Coq7p remains phosphorylated in fermentative conditions and becomes dephosphorylated when respiratory metabolism is induced. The substitution of phosphorylated residues to alanine dramatically increases Q6 levels (256%). Conversely, substitution with negatively charged residues decreases Q6 content (57%). These modifications produced in Coq7p also alter the ratio between DMQ6 and Q6 itself, indicating that Coq7p phosphorylation state is a regulatory mechanism for Q6 synthesis.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...