Coq3 O-methyltransferase carries out both O-methylation steps in coenzyme Q (ubiquinone) biosynthesis. The degree to which Coq3 O-methyltransferase activity and expression are dependent on the other seven COQ gene products has been investigated. A panel of yeast mutant strains harboring null mutations in each of the genes required for coenzyme Q biosynthesis (COQ1-COQ8) have been prepared. Mitochondria have been isolated from each member of the yeast coq mutant collection, from the wild-type parental strains and from respiratory deficient mutants harboring deletions in ATP2 or COR1 genes. These latter strains constitute Q-replete, respiratory deficient controls. Each of these mitochondrial preparations has been analyzed for COQ3-encoded O-methyltransferase activity and steady state levels of Coq3 polypeptide. The findings indicate that the presence of the other COQ gene products is required to observe normal levels of O-methyltransferase activity and the Coq3 polypeptide. However, COQ3 steady state RNA levels are not decreased in any of the coq mutants, relative to either wild-type or respiratory deficient control strains, suggesting either a decreased rate of translation or a decreased stability of the Coq3 polypeptide. These data are consistent with the involvement of the Coq polypeptides (or the Q-intermediates formed by the Coq polypeptides) in a multi-subunit complex. It is our hypothesis that a deficiency in any one of the COQ gene products results in a defective complex in which the Coq3 polypeptide is rendered unstable.
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| Gene/Complex | Qualifier | Gene Ontology Term | Annotation Extension | Evidence | Source | Assigned On |
|---|---|---|---|---|---|---|
| COQ1 | is active in | mitochondrion | IMP | SGD | 2023-12-12 | |
| COQ1 | located in | mitochondrion | IMP | SGD | 2013-08-07 | |
| COQ3 | located in | mitochondrion | IDA | SGD | 2013-08-07 |
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| Gene | Phenotype | Experiment Type | Mutant Information | Strain Background | Chemical | Details |
|---|---|---|---|---|---|---|
| COQ2 | protein/peptide accumulation: decreased Reporter: Coq3p | classical genetics | null Allele: coq2-Δ | CEN.PK | ||
| CAT5 | protein/peptide accumulation: decreased Reporter: Coq3p | classical genetics | null Allele: cat5-Δ | CEN.PK | ||
| COQ1 | protein/peptide accumulation: decreased Reporter: Coq3p | classical genetics | null Allele: coq1-Δ | CEN.PK | ||
| COQ8 | protein/peptide accumulation: decreased Reporter: Coq3p | classical genetics | null Allele: coq8-Δ | CEN.PK | ||
| COQ5 | protein/peptide accumulation: decreased Reporter: Coq3p | classical genetics | null Allele: coq5-Δ | CEN.PK | ||
| COQ2 | respiratory growth: absent | classical genetics | null Allele: coq2-Δ | CEN.PK | ||
| CAT5 | respiratory growth: absent | classical genetics | null Allele: cat5-Δ | CEN.PK | ||
| COQ6 | respiratory growth: absent | classical genetics | null Allele: coq6-Δ | CEN.PK | ||
| COQ1 | respiratory growth: absent | classical genetics | null Allele: coq1-Δ | CEN.PK | ||
| COQ8 | respiratory growth: absent | classical genetics | null Allele: coq8-Δ | CEN.PK |