Ribosomal RNA chain growth rate and RNA labeling patterns in Escherichia coli[formula omitted

Abstract

The labeling patterns of total, stable and unstable RNA in Escherichia coli B/r growing at a rate of 2·1 doublings/hr were analyzed both theoretically and experimentally. The experiments employ the antibiotic rifampicin which specifically inhibits initiation of RNA chains without interfering with elongation and completion of nascent RNA chains. The results indicate that stable RNA accounts for 71 % of the instantaneous rate of total RNA synthesis while unstable RNA accounts for the remaining 29 %. The kinetics of labeling unstable RNA were observed to be consistent with an average half life for unstable RNA of 2·8 min. Furthermore, the transcription time of the 16S-23S-5S ribosomal genes (4620 nucleotides) was estimated to be 44 sec, which corresponds to a ribosomal RNA chain growth rate of 105 nucleotides per sec.