InterPro domain: IPR020598

The bacterial enzyme KsgA catalyses the transfer of a total of four methyl groups from S-adenosyl-l-methionine (S-AdoMet) to two adjacent adenosine bases in 16S rRNA. This enzyme and the resulting modified adenosine bases appear to be conserved in all species of eubacteria, eukaryotes, and archaea, and in eukaryotic organelles. Bacterial resistance to the aminoglycoside antibiotic kasugamycin involves inactivation of KsgA and resulting loss of the dimethylations, with modest consequences to the overall fitness of the organism. In contrast, the yeast ortholog, Dim1, is essential. In Saccharomyces cerevisiae (Baker's yeast), and presumably in other eukaryotes, the enzyme performs a vital role in pre-rRNA processing in addition to its methylating activity [ 1 ]. Another orthologue is the eukaryotic transcription factor B (TFB), which has a second function; this enzyme is a nuclear-encoded mitochondrial transcription factor and is essential for mitochondrial gene expression [ 2 ]. The best conserved region in these enzymes is located in the N-terminal section and corresponds to a region that is probably involved in S-adenosyl methionine (SAM) binding domain.

This entry represents the N-terminal domain of rRNA adenine methylase transferases.

1. Crystal structure of KsgA, a universally conserved rRNA adenine dimethyltransferase in Escherichia coli. J. Mol. Biol. 339, 337-53
2. Structural basis for S-adenosylmethionine binding and methyltransferase activity by mitochondrial transcription factor B1. Nucleic Acids Res. 41, 7947-59