<p>This family of proteins represent the rRNA adenine dimethylases (e.g. KsgA).</p><p>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 yeast, and presumably in other eukaryotes, the enzyme performs a vital role in pre-rRNA processing in addition to its methylating activity. 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.</p><p>The crystal structure of KsgA from <taxon tax_id="562">Escherichia coli</taxon> has been solved to a resolution of 2.1A. It bears a strong similarity to the crystal structure of ErmC' from <taxon tax_id="1422">Bacillus stearothermophilus</taxon> (Geobacillus stearothermophilus) and a lesser similarity to the yeast mitochondrial transcription factor, sc-mtTFB [<cite idref="PUB00014820"/>].</p> Ribosomal RNA adenine dimethylase