Protein Domain : Ribosomal RNA adenine methyltransferase KsgA/Erm IPR001737

Type	Family
Description	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 []. 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 []. 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.rRNA adenine N-6-methyltransferases Erm methylate a single adenosine base in 23S rRNA. They confer resistance to the MLS-B group of antibiotics [ , ]. Despite their sequence similarity to KsgA, the two enzyme families have strikingly different levels of regulation that remain to be elucidated.
Short Name	KsgA/Erm