Yeast COQ4 encodes a mitochondrial protein required for coenzyme Q synthesis.
The COQ4 gene coding for a component of the coenzyme Q biosynthetic pathway in the yeast Saccharomyces cerevisiae was cloned by a functional complementation of a Q-deficient mutant strain. Yeast coq4 mutant strains harboring the COQ4 gene on either single- or multicopy plasmids acquired the ability to grow on media containing a nonfermentable carbon source, synthesize Q(6), and respire. COQ4 encodes a polypeptide containing 335 amino acids with a calculated molecular mass of 38.6 kDa. By Western blot analysis with a specific antiserum, Coq4p was shown to peripherally associate with the matrix face of the mitochondrial inner membrane. The putative mitochondrial-targeting sequence present at the amino-terminus of the polypeptide efficiently imported it to mitochondria in a membrane-potential-dependent manner. Steady-state levels of COQ4 mRNA were increased during growth on glycerol-containing medium, in accordance with a function in Q biosynthesis. The function of Coq4p is unknown, although its presence is required to maintain a steady-state level of Coq7p, another component of the Q biosynthetic pathway. The results presented here, along with those available from literature, are discussed in light of the recently proposed existence of a multisubunit complex functioning in Q biosynthesis (A. Y. Hsu, T. Q. Do, P. T. Lee, and C. F. Clarke, 2000, Biochim. Biophys. Acta 1484, 287-297).
Belogrudov
G I
GI
Department of Chemistry and Biochemistry, University of California at Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, USA.
Lee
P T
PT
Jonassen
T
T
Hsu
A Y
AY
Gin
P
P
Clarke
C F
CF
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal; D062385:Hydroxybenzoates / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D010101:Oxygen Consumption; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D014315:Triterpenes / Q000378:metabolism; D014451:Ubiquinone / Q000096:biosynthesis* / Q000235:genetics*
C433869:COQ4 protein, S cerevisiae; D017931:DNA Primers; D005656:Fungal Proteins; D062385:Hydroxybenzoates; D024101:Mitochondrial Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D014315:Triterpenes; D014451:Ubiquinone; C094743:3-hexaprenyl-4-hydroxybenzoic acid