Presence of precursor ribosome in the ribosomal preparation from chloramphenicol-treated Escherichia coli ΑΒ301/Ι05 (RNase III – ).

ABSTRACT

On sucrose gradient centrifugation, the ribosomal preparation from chloramphenicoltreated 32P labelled Escherichia coli AB301/105 (RNase III¯ ) showed the presence of a radioactive peak moving slower than the 70S ribosome; this peak disappeared on treatment with RNase III. The presence of precursor 30S RNA was shown in such preparations by affinity chromatography on a lysine-sepharose 4B column as well as polyacrylamide gel electrophoresis. Dialysis against low Mg2± concentration followed by sucrose density gradient electrophoresis. Dialysis against dissociation of 70S ribosome into its subunits, did not lead to the dissociation of the precursor ribosome. However, the dissociation took place upon treatment with RNase III. A tentative model of coupled rRNA transcription and ribosome assembly has been presented.