InterPro domain: IPR004147

This entry represents a domain found in Escherichia coli UbiB, known in Providencia stuartii as Aarf, which is required for ubiquinone (CoQ) biosynthesis [ 1 , 2 , 3 ]. Some proteins with this domain are described as aarF domain-containing protein kinases (ADCKs). This domain is also found in yeast ABC1 proteins ( P27697 ) required for function of the mitochondrial bc1 complex [ 4 ], in which CoQ functions as an essential cofactor.

The function of these proteins is not clear. Along with ABC1, UbiB is part of a large family of proteins that contain motifs found in eukaryotic-type protein kinases [ 5 ], but is not known if they have kinase activity and how this would relate to their requirement for the monoxygenase step in CoQ synthesis. A role in regulation of this step by phosphorylation has been speculated [ 6 ].

1. Identification of Escherichia coli ubiB, a gene required for the first monooxygenase step in ubiquinone biosynthesis. J. Bacteriol. 182, 5139-46
2. Identification and characterization of aarF, a locus required for production of ubiquinone in Providencia stuartii and Escherichia coli and for expression of 2'-N-acetyltransferase in P. stuartii. J. Bacteriol. 180, 128-35
3. ubiI, a new gene in Escherichia coli coenzyme Q biosynthesis, is involved in aerobic C5-hydroxylation. J. Biol. Chem. 288, 20085-92
4. ABC1, a novel yeast nuclear gene has a dual function in mitochondria: it suppresses a cytochrome b mRNA translation defect and is essential for the electron transfer in the bc 1 complex. EMBO J. 10, 2023-31
5. Novel families of putative protein kinases in bacteria and archaea: evolution of the "eukaryotic" protein kinase superfamily. Genome Res. 8, 1038-47