Mitochondrial 5-demethoxyubiquinone hydroxylase (DMQ hydroxylase), also known as coenzyme Q7, hydroxylase, is an enzyme that in humans is encoded by the COQ7 gene. The clk-1 (clock-1) gene encodes this protein that is necessary for ubiquinone biosynthesis in the worm Caenorhabditis elegans and other eukaryotes. The mouse version of the gene is called mclk-1 and the human, fruit fly and yeast homolog COQ7 (coenzyme Q biosynthesis protein 7).[5][6]
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CLK-1 is not to be confused with the unrelated human protein CLK1 which plays a role in RNA splicing.
The protein has two repeats of approximately 90 amino acids, that contain two conserved motifs predicted to be important for coordination of iron. The structure and function of the gene are highly conserved among different species.[7]
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).[8]
Ubiquinone is a small redox active lipid that is found in most cellular membranes where it acts as a cofactor in numerous cellular redox processes, including mitochondrial electron transport. As a cofactor, 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.
It has been shown that mutations in the gene are associated with increased lifespan.[5][7] 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.[9]
CLK-1 and COQ7 predominantly localise to mitochondria to participate in the ubiquinone biosynthetic pathway which is found there. However, a small pool of CLK-1 and COQ7 translocates to the nucleus in response to the production of ROS by normally functioning mitochondria in both worms and human cells, respectively.[10] Translocation of CLK-1 and COQ7 represents a mitochondrial to nuclear retrograde signalling pathway that acts to suppress mitochondrial stress responses. The mitochondrial and nuclear pools of CLK-1 are thought to contribute independently to worm lifespan regulation. The nuclear form of CLK-1 and COQ7 is thought to regulate gene expression through an unidentified mechanism.
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.
- Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID 8125298.
- Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID 9373149.
- Jonassen T, Proft M, Randez-Gil F, et al. (1998). "Yeast Clk-1 homologue (Coq7/Cat5) is a mitochondrial protein in coenzyme Q synthesis". J. Biol. Chem. 273 (6): 3351–7. doi:10.1074/jbc.273.6.3351. PMID 9452453.
- Asaumi S, Kuroyanagi H, Seki N, Shirasawa T (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.
- Vajo Z, King LM, Jonassen T, et al. (2000). "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. S2CID 13800512.
- Hartley JL, Temple GF, Brasch MA (2001). "DNA cloning using in vitro site-specific recombination". Genome Res. 10 (11): 1788–95. doi:10.1101/gr.143000. PMC 310948. PMID 11076863.
- Wiemann S, Weil B, Wellenreuther R, et al. (2001). "Toward a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs". Genome Res. 11 (3): 422–35. doi:10.1101/gr.GR1547R. PMC 311072. PMID 11230166.
- Simpson JC, Wellenreuther R, Poustka A, et al. (2001). "Systematic subcellular localization of novel proteins identified by large-scale cDNA sequencing". EMBO Rep. 1 (3): 287–92. doi:10.1093/embo-reports/kvd058. PMC 1083732. PMID 11256614.
- Stenmark P, Grünler J, Mattsson J, et al. (2001). "A new member of the family of di-iron carboxylate proteins. Coq7 (clk-1), a membrane-bound hydroxylase involved in ubiquinone biosynthesis". J. Biol. Chem. 276 (36): 33297–300. doi:10.1074/jbc.C100346200. PMID 11435415.
- Takahashi M, Asaumi S, Honda S, et al. (2001). "Mouse coq7/clk-1 orthologue rescued slowed rhythmic behavior and extended life span of clk-1 longevity mutant in Caenorhabditis elegans". Biochem. Biophys. Res. Commun. 286 (3): 534–40. doi:10.1006/bbrc.2001.5439. PMID 11511092.
- Rea S (2002). "CLK-1/Coq7p is a DMQ mono-oxygenase and a new member of the di-iron carboxylate protein family". FEBS Lett. 509 (3): 389–94. doi:10.1016/S0014-5793(01)03099-X. PMID 11749961. S2CID 28650687.
- Strausberg RL, Feingold EA, Grouse LH, et al. (2003). "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences". Proc. Natl. Acad. Sci. U.S.A. 99 (26): 16899–903. Bibcode:2002PNAS...9916899M. doi:10.1073/pnas.242603899. PMC 139241. PMID 12477932.
- Ota T, Suzuki Y, Nishikawa T, et al. (2004). "Complete sequencing and characterization of 21,243 full-length human cDNAs". Nat. Genet. 36 (1): 40–5. doi:10.1038/ng1285. PMID 14702039.
- Wiemann S, Arlt D, Huber W, et al. (2004). "From ORFeome to biology: a functional genomics pipeline". Genome Res. 14 (10B): 2136–44. doi:10.1101/gr.2576704. PMC 528930. PMID 15489336.
- Mehrle A, Rosenfelder H, Schupp I, et al. (2006). "The LIFEdb database in 2006". Nucleic Acids Res. 34 (Database issue): D415–8. doi:10.1093/nar/gkj139. PMC 1347501. PMID 16381901.
