A number of enzymes responsible for the dimethylation of adenosines in
ribosomal RNAs (EC 188.8.131.52) have been found [1,2] to be evolutionary related.
These enzymes are:
Bacterial 16S rRNA dimethylase (gene ksgA), which acts in the biogenesis
of ribosomes by catalyzing the dimethylation of two adjacent adenosines in
the loop of a conserved hairpin near the 3'-end of 16S rRNA. Inactivation
of ksgA leads to resistance to the aminoglycoside antibiotic kasugamycin.
Yeast 18S rRNA dimethylase (gene DIM1), which is functionally similar to
ksgA and that dimethylates twin adenosines in the 3'-end of 18S rRNA.
Bacterial 'erm' methylases. These enzymes confer resistance to macrolide-
lincosamide-streptogramin B (MLS) antibiotics - such as erythromycin - by
dimethylating the adenine residue at position 2058 of 23S rRNA thus
resulting in a reduced affinity between ribosomes and the MLS antibiotics.
Caenorhabditis elegans hypothetical protein EO2H1.1.
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.
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