InterPro domain: IPR034646

UbiB kinases are present in archaea, bacteria and eukaryote. The founding member of the UbiB family, UbiB from Escherichia coli, is required for the aerobic biosynthesis of coenzyme Q (CoQ). In eukaryotes, UbiB homologues are found exclusively in mitochondria and plastids. This entry represents the UbiB domain found in eukaryotes and some bacteria, but not in E. coli and related species [ 1 ].

This domain is found in the atypical yeast protein kinase Abc1p (also called Coq8p), its human homologue ADCK3 (also called COQ8A), and similar proteins. Abc1p is required for the biosynthesis of Coenzyme Q (ubiquinone or Q), which is an essential lipid component in respiratory electron and proton transport. It is necessary for the formation of a multi-subunit Q-biosynthetic complex and may also function in the regulation of Q synthesis. Human ADCK3 is able to rescue defects in Q synthesis and the phosphorylation state of Coq proteins in yeast Abc1 (or Coq8) mutants [ 2 ]. Mutations in ADCK3 cause progressive cerebellar ataxia and atrophy due to Q10 deficiency [ 3 , 4 , 5 , 6 ].

In algae and higher plants, ABC1 kinases have proliferated to more than 15 subfamilies, most of which are located in plastids or mitochondria [ 7 , 8 ]. Subfamily 13 (ABC1K13) of plant ABC1 kinases belongs in this group with yeast Abc1p and human ADCK3. ABC1 kinases are not related to the ATP-binding cassette (ABC) membrane transporter family.

1. Mitochondrial ADCK3 employs an atypical protein kinase-like fold to enable coenzyme Q biosynthesis. Mol. Cell 57, 83-94
2. Expression of the human atypical kinase ADCK3 rescues coenzyme Q biosynthesis and phosphorylation of Coq polypeptides in yeast coq8 mutants. Biochim. Biophys. Acta 1811, 348-60
3. Adult-onset cerebellar ataxia due to mutations in CABC1/ADCK3. J. Neurol. Neurosurg. Psychiatr. 83, 174-8
4. Nonsense mutations in CABC1/ADCK3 cause progressive cerebellar ataxia and atrophy. Mitochondrion 10, 510-5
5. ADCK3, an ancestral kinase, is mutated in a form of recessive ataxia associated with coenzyme Q10 deficiency. Am. J. Hum. Genet. 82, 661-72
6. CABC1 gene mutations cause ubiquinone deficiency with cerebellar ataxia and seizures. Am. J. Hum. Genet. 82, 623-30
7. ABC1K atypical kinases in plants: filling the organellar kinase void. Trends Plant Sci. 17, 546-55
8. Characterization of an Abc1 kinase family gene OsABC1-2 conferring enhanced tolerance to dark-induced stress in rice. Gene 498, 155-63