The clk-1 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 encodes an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 (demethoxyubiquinone mono-oxygenase) that is necessary for ubiquinone biosynthesis in the worm C. elegans

Caenorhabditis elegans

Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...

and other eukaryote

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s. The mouse

Mouse

A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...

 version of the gene is called mclk1 and the human, fruit fly and yeast homolog COQ7 (Coenzyme Q biosynthesis protein 7 homolog).

Clk-1 is not to be confused with the unrelated CLK1

CLK1

Dual specificity protein kinase CLK1 is an enzyme that in humans is encoded by the CLK1 gene.-Further reading:...

 human gene which plays a role in RNA splicing

RNA splicing

In molecular biology and genetics, splicing is a modification of an RNA after transcription, in which introns are removed and exons are joined. This is needed for the typical eukaryotic messenger RNA before it can be used to produce a correct protein through translation...

.

Structure

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.

The protein has two repeats of about 90 amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s, 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.

The C. elegans

Caenorhabditis elegans

Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...

protein contains 187 amino acid residues (20 kilodaltons), the human homolog 217 amino acid residues (24 kilodaltons, gene consisting of six exon

Exon

An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...

s spanning 11 kb and located on chromosome 16).

Function

Ubiquinone is a small redox active lipid

Lipid

Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

 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

Reactive oxygen species

Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....

 (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

Life expectancy

Life expectancy is the expected number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience...

. 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.