The COQ5 Gene Encodes a Yeast Mitochondrial Protein Necessary for Ubiquinone Biosynthesis and the Assembly of the Respiratory Chain

Abstract

Saccharomyces cerevisiae is a facultative anaerobe capable of meeting its energy requirements by fermentation and is thus an ideal system for studying the biogenesis of respiring mitochondria. We have isolated a respiration-deficient mutant exhibiting a pleiotropic loss of the mitochondrial electron transport chain. The corresponding wild-type gene, COQ5, was cloned, sequenced, and able to restore respiratory growth. Deletion of the chromosomal COQ5 gene results in a respiration deficiency and reduced levels of respiratory protein components. Exogenously added decylubiquinone can partially restore electron transport chain function to mitochondrial membranes from the deletion mutant. The COQ5 nucleotide sequence predicts a polypeptide of 307 amino acids containing a mitochondrial targeting signal. COQ5p is 43% identical to the polypeptide predicted by the Escherichia coli open reading frame, o251 (1). The COQ5 gene, when introduced into E. coli, complements the respiratory deficiency of an ubiE mutant that maps near o251, suggesting that it is the yeast homolog of the ubiE gene product. We conclude that the COQ5 gene encodes the mitochondria-localized 2-hexaprenyl-6-methoxy-1,4-benzoquinone methyltransferase of the yeast ubiquinone biosynthetic pathway.

Functional Analysis of Two Solanesyl Diphosphate Synthases fromArabidopsis thaliana

“…6,[32][33][34][35][36] Among plant ubiquinone biosynthetic enzymes, A. thaliana 3,4-dihydroxy-5-trans-polyprenyl-benzoate methyltransferase and A. thaliana 4-hydroxy benzoate polyprenyltransferase have thus far been characterized, and both enzymes have been shown to be localized in mitochondria. 37,38) 4-Hydroxy benzoate polyprenyltransferase catalyzes attachment of the polyprenyl group to 4-hydroxy benzoate to yield 4-hydroxy-3-polyprenyl benzoate.…”

Involvement of a Broccoli COQ5 Methyltransferase in the Production of Volatile Selenium Compounds

“…COQ5/UbiE methyltransferases are required for ubiquinone biosynthesis (Dibrov et al, 1997;Lee et al, 1997). The yeast strain TCM7 is a coq5 null mutant that can not grow on YPG medium with glycerol as the sole carbon source (Dibrov et al, 1997).…”

“…The yeast strain TCM7 is a coq5 null mutant that can not grow on YPG medium with glycerol as the sole carbon source (Dibrov et al, 1997). To examine whether the BoCOQ5-2 cDNA encoded a protein with COQ5 methyltransferase function, the coding region of BoCOQ5-2 was cloned into the yeast expression vector pFL61 (Minet et al, 1992).…”

“…The resulting constructs, termed pFL-BoCOQ5-2 and pFL-COQ5, were mobilized into yeast coq5 mutant strain TCM7, kindly provided by Dr. Bernard D. Lemire (University of Alberta, Canada; Dibrov et al, 1997). Transformants were selected on the dropout medium depleted of uracil and then plated on YPD medium (containing 2% Glc) and YPG (containing 2% glycerol), respectively, for complementation of the mutant phenotype.…”

“…COQ5 genes encode C-methyltransferases involved in the biosynthesis of ubiquinone or coenzyme Q (Dibrov et al, 1997;Lee et al, 1997). Ubiquinone is an important lipid-soluble compound found in membranes of almost all living species.…”