7o5h
Ribosomal methyltransferase KsgA bound to small ribosomal subunit
Structural highlights
FunctionRSMA_ECOLI Specifically dimethylates two adjacent adenosines (A1518 and A1519) in the loop of a conserved hairpin near the 3'-end of 16S rRNA in the 30S particle. May play a critical role in biogenesis of 30S subunits. Has also a DNA glycosylase/AP lyase activity that removes C mispaired with oxidized T from DNA, and may play a role in protection of DNA against oxidative stress.[1] [2] [3] Publication Abstract from PubMedBiogenesis of ribosomal subunits involves enzymatic modifications of rRNA that fine-tune functionally important regions. The universally conserved prokaryotic dimethyltransferase KsgA sequentially modifies two universally conserved adenosine residues in helix 45 of the small ribosomal subunit rRNA, which is in proximity of the decoding site. Here we present the cryo-EM structure of Escherichia coli KsgA bound to an E. coli 30S at a resolution of 3.1 A. The high-resolution structure reveals how KsgA recognizes immature rRNA and binds helix 45 in a conformation where one of the substrate nucleotides is flipped-out into the active site. We suggest that successive processing of two adjacent nucleotides involves base-flipping of the rRNA, which allows modification of the second substrate nucleotide without dissociation of the enzyme. Since KsgA is homologous to the essential eukaryotic methyltransferase Dim1 involved in 40S maturation, these results have also implications for understanding eukaryotic ribosome maturation. Structural basis of successive adenosine modifications by the conserved ribosomal methyltransferase KsgA.,Stephan NC, Ries AB, Boehringer D, Ban N Nucleic Acids Res. 2021 Jun 21;49(11):6389-6398. doi: 10.1093/nar/gkab430. PMID:34086932[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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