title: COQ2 is a candidate for the structural gene encoding para-hydroxybenzoate:polyprenyltransferase.
abstract: Coenzyme Q functions as a lipid-soluble electron carrier in eukaryotes. In Saccharomyces cerevisiae, the enzymes responsible for the assembly of the polyisoprenoid side chain and subsequent transfer to para-hydroxybenzoate (PHB) are encoded by the nuclear genes COQ1 and COQ2, respectively. Yeast mutants defective in coenzyme Q biosynthesis are respiratory defective and provide a useful tool to study this non-sterol branch of the isoprenoid biosynthetic pathway. We isolated a 5.5-kilobase genomic DNA fragment that was able to functionally complement a coq2 strain. Additional complementation analyses located the COQ2 gene within a 2.1-kilobase HindIII-BglII restriction fragment. Sequence analyses revealed the presence of a 1,116-base pair open reading frame coding for a predicted protein of 372 amino acids and a molecular mass of 41,001 daltons. The amino acid sequence exhibits a typical amino-terminal mitochondrial leader sequence and six potential membrane-spanning domains. Primer extension and Northern analyses indicate the gene is transcriptionally active. Transformation of a coq2 strain with the 2.1-kilobase HindIII-BglII genomic restriction fragment on a multicopy plasmid restores PHB:polyprenyltransferase activity to wild-type levels. Disruption of the chromosomal COQ2 gene indicates the gene is not essential for viability, yet is required for PHB:polyprenyltransferase activity and respiratory function. In addition, the deduced amino acid sequence of PHB:polyprenyltransferase contains a putative allylic polyprenyl diphosphate-binding site. The presence of this aspartate-rich domain in a number of functionally distinct proteins which utilize polyprenyl diphosphate substrates is reported.
authors.affiliation: Department of Biological Chemistry, UCLA School of Medicine 90024.
authors.forename: M N
authors.initials: MN
authors.lastname: Ashby
authors.forename: S Y
authors.initials: SY
authors.lastname: Kutsunai
authors.forename: S
authors.initials: S
authors.lastname: Ackerman
authors.forename: A
authors.initials: A
authors.lastname: Tzagoloff
authors.forename: P A
authors.initials: PA
authors.lastname: Edwards
mesh_terms: D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004271:DNA, Fungal; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014166:Transferases / Q000235:genetics* / Q000378:metabolism; D014451:Ubiquinone / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D014451:Ubiquinone; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C021386:4-hydroxybenzoate polyprenyltransferase