| Abstract
| - The methyltransferase that forms m5C967 in Escherichia coli small subunit ribosomal RNAhas been purified, cloned, and characterized. The gene was identified from the N-terminal sequence ofthe purified enzyme. The gene is a fusion of two open reading frames, fmu and fmv, previously believedto be distinct due to a DNA sequencing error. The gene, here named rsmB, encodes a 429-amino acidprotein that has a number of homologues in prokaryotes, Archaea, and eukaryotes. C-Terminal sequencingof the overexpressed and affinity-purified protein by mass spectrometry methods verified the sequenceexpected for the gene product. The recombinant protein exhibited the same specificity as the previouslydescribed native enzyme; that is, it formed only m5C and only at position 967. C1407, which is also m5Cin natural 16S RNA, was not methylated. In vitro, the enzyme only recognized free 16S RNA. 30Sribosomal subunits were not a substrate. There was no requirement for added magnesium, suggesting thatextensive secondary or tertiary structure in the RNA substrate may not be a requirement for recognition.
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