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Coenzyme Q7 homolog, ubiquinone (yeast)
Symbols COQ7 ; CAT5; CLK-1; CLK1
External IDs OMIM601683 MGI107207 HomoloGene6953 GeneCards: COQ7 Gene
EC number 1.14.13.-
RNA expression pattern
PBB GE COQ7 209746 s at tn.png
PBB GE COQ7 209745 at tn.png
PBB GE COQ7 210820 x at tn.png
More reference expression data
Species Human Mouse
Entrez 10229 12850
Ensembl ENSG00000167186 ENSMUSG00000030652
UniProt Q99807 P97478
RefSeq (mRNA) NM_001190983 NM_009940
RefSeq (protein) NP_001177912 NP_034070
Location (UCSC) Chr 16:
19.08 – 19.09 Mb
Chr 7:
118.51 – 118.53 Mb
PubMed search [1] [2]

The clk-1 (Clock abnormal protein 1) gene encodes an enzyme (demethoxyubiquinone mono-oxygenase) that is necessary for ubiquinone biosynthesis in the worm Caenorhabditis elegans and other eukaryotes. The mouse version of the gene is called mclk1 and the human, fruit fly and yeast homolog COQ7 (Coenzyme Q biosynthesis protein 7 homolog).[1][2]

Clk-1 is not to be confused with the unrelated CLK1 human gene which plays a role in RNA splicing.


In 1999, Zoltan Vajo et al. cloned COQ7 from human heart. They found that the human COQ7 protein contains 179 amino acids, is mostly helical, and contains an alpha-helical membrane insertion. It has a potential N-glycosylation site, a phosphorylation site for protein kinase C and another for casein kinase II, and 3 N-myristoylation sites. Northern blot analysis detected 3 transcripts; a 1-kb transcript was predominant in heart, and a 3-kb transcript was predominant in skeletal muscle, kidney, and pancreas.[3]

The protein has two repeats of about 90 amino acids, that contain two conserved motifs. One of these DXEXXH may be part of an enzyme active site. The structure and function of the gene are highly conserved among different species.[4]

The C. elegans protein contains 187 amino acid residues (20 kilodaltons), the human homolog 217 amino acid residues (24 kilodaltons, gene consisting of six exons spanning 11 kb and located on chromosome 16).[5]


Ubiquinone is a small redox active lipid that is found in all membranes and that is a co-factor in numerous cellular redox processes, including mitochondrial electron transport. As a co-factor, ubiquinone is often involved in processes that produce reactive oxygen species (ROS). In addition, ubiquinone is one of the main endogenous antioxidants of the cell. The CLK-1 enzyme is responsible for the hydroxylation of 5-demethoxyubiquinone to 5-hydroxyubiquinone.

When ubiquinone biosynthesis is interrupted by the absence of the enzyme, cells accumulate an intermediate of ubiquinone biosynthesis, demethoxyubiquinone (DMQ).

It has been shown that mutations in the gene are associated with increased life span.[1][4] Defects of the gene slow down a variety of developmental and physiological processes, including the cell cycle, embryogenesis, post-embryonic growth, rhythmic behaviors and aging.[6]


  1. ^ a b Ewbank JJ, Barnes TM, Lakowski B, Lussier M, Bussey H, Hekimi S (February 1997). "Structural and functional conservation of the Caenorhabditis elegans timing gene clk-1". Science 275 (5302): 980–3. doi:10.1126/science.275.5302.980. PMID 9020081. 
  2. ^ "Entrez Gene: COQ7 coenzyme Q7 homolog, ubiquinone (yeast)". 
  3. ^ Vajo Z, King LM, Jonassen T, Wilkin DJ, Ho N, Munnich A, Clarke CF, Francomano CA (October 1999). "Conservation of the Caenorhabditis elegans timing gene clk-1 from yeast to human: a gene required for ubiquinone biosynthesis with potential implications for aging". Mamm. Genome 10 (10): 1000–4. doi:10.1007/s003359901147. PMID 10501970. 
  4. ^ a b Liu X, Jiang N, Hughes B, Bigras E, Shoubridge E, Hekimi S (October 2005). "Evolutionary conservation of the clk-1-dependent mechanism of longevity: loss of mclk1 increases cellular fitness and lifespan in mice". Genes Dev. 19 (20): 2424–34. doi:10.1101/gad.1352905. PMC 1257397. PMID 16195414. 
  5. ^ Asaumi S, Kuroyanagi H, Seki N, Shirasawa T (June 1999). "Orthologues of the Caenorhabditis elegans longevity gene clk-1 in mouse and human". Genomics 58 (3): 293–301. doi:10.1006/geno.1999.5838. PMID 10373327. 
  6. ^ Felkai S, Ewbank JJ, Lemieux J, Labbé JC, Brown GG, Hekimi S (April 1999). "CLK-1 controls respiration, behavior and aging in the nematode Caenorhabditis elegans". EMBO J. 18 (7): 1783–92. doi:10.1093/emboj/18.7.1783. PMC 1171264. PMID 10202142. 

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