Different cleavage specificities of RNases III from Rhodobacter capsulatus and Escherichia coli.
23S rRNA in Rhodobacter capsulatus shows endoribonuclease III (RNase III)-dependent fragmentation in vivo at a unique extra stem-loop extending from position 1271 to 1331. RNase III is a double strand (ds)-specific endoribonuclease. This substrate preference is mediated by a double-stranded RNA binding domain (dsRBD) within the protein. Although a certain degree of double strandedness is a prerequisite, the question arises what structural features exactly make this extra stem-loop an RNase III cleavage site, distinguishing it from the plethora of stem-loops in 23S rRNA? We used RNase III purified from R.capsulatus and Escherichia coli, respectively, together with well known substrates for E.coli RNase III and RNA substrates derived from the special cleavage site in R.capsulatus 23S rRNA to study the interaction between the Rhodobacter enzyme and the fragmentation site. Although both enzymes are very similar in their amino acid sequence, they exhibit significant differences in binding and cleavage of these in vitro substrates.
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Institut für Mikro- und Molekularbiologie der Justus-Liebig-Universität Giessen, Frankfurter Strasse 107,35392 Giessen, Germany.
Rauhut
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D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D016354:Rhodobacter capsulatus / Q000201:enzymology*; D043244:Ribonuclease III; D013045:Species Specificity; D013379:Substrate Specificity
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D004722:Endoribonucleases; D043244:Ribonuclease III; C468366:ribonuclease III, E coli