This entry represents18S rRNA aminocarboxypropyltransferases Tsr3 and its homologues. Tsr3 from fungi and animals are responsible for 18S rRNA hypermodification. It introduces the acp group to the hypermodified m1acp3psi nucleotide at position 1191 (yeast)/ 1248 (humans) of 18S rRNA. The crystal structure of archaeal Tsr3 homologues revealed the same fold as in SPOUT-class RNA-methyltransferases but a distinct SAM binding mode. This unique SAM binding mode explains why Tsr3 transfers the acp and not the methyl group of SAM to its substrate. Structurally, Tsr3 therefore represents a novel class of acp transferase enzymes [].
This domain can be found in the eukaryotic ribosome biogenesis protein Tsr3, which is involved in ribosomal RNA biogenesis []. This domain is also found in the C terminus of Tsr3 homologues from archaea. It is usually associated with a putative metal-binding region in RNase L inhibitor, RLI (). Tsr3 from fungi and animals are responsible for 18S rRNA hypermodification. The Crystal structure of archaeal Tsr3 homologues revealed the same fold as in SPOUT-class RNA-methyltransferases but a distinct SAM binding mode. This unique SAM binding mode explains why Tsr3 transfers the acp and not the methyl group of SAM to its substrate. Structurally, Tsr3 therefore represents a novel class of acp transferase enzymes [].
