%0 Journal Article
%T Functional interaction between RNase III and the Escherichia coli ribosome
%A ¨šlar Allas
%A Aivar Liiv
%A Jaanus Remme
%J BMC Molecular Biology
%D 2003
%I BioMed Central
%R 10.1186/1471-2199-4-8
%X We have analyzed RNase III cleavage sites around both ends of pre-23 S rRNA in the ribosome and in the protein-free pre-rRNA. It was found that in the protein-free pre-23 S rRNA the main cleavage site is at position (-7) in respect of the mature 5' end. When pre-23 S rRNA was in 70 S ribosomes or in 50 S subunits, the RNase III cleavage occurred at position (-3). We have demonstrated that RNase III interacts with both ribosomal subunits and with even higher affinity with 70 S ribosomes. Association of RNase III with 70 S ribosomes cannot be dissociated by poly(U) RNA indicating that the binding is specific.In addition to the primary and secondary structural elements in RNA, protein binding to substrate RNA can be a determinant of the RNase III cleavage site.In Escherichia coli, each of the seven rRNA operons is transcribed as a 30 S precursor containing functional gene products ¨C 16 S, 23 S, 5 S and tRNA(s). In addition, 30 S precursor molecules contain extra sequences in the beginning and end of structural genes and in between, as well. These additional sequences are removed by a series of processing events [1]. Enzymes involved in rRNA processing have been the subject of extensive studies, but a full understanding of this important process is still incomplete [reviewed in [1,2]]).RNase III is the best studied enzyme involved in rRNA processing. RNase III is highly conserved in the eubacteria and orthologs occur in fungi, plants and animals [3,4]. In E. coli RNase III is encoded by the rnc gene [5], which maps at 55 minutes. It is a double-stranded RNA specific enzyme [6], which is active as a 52 kDa homodimer [7] and requires a divalent metal ion (preferably Mg2+) for activity [8]. In addition to the secondary structure of substrate RNA, both positive (determinants) and negative (antideterminants) sequence elements are important in determining the cleavage site [2].In Escherichia coli, sequences flanking both 16 S RNA and 23 S RNA contain complementary sequence tr
%U http://www.biomedcentral.com/1471-2199/4/8