| Primary Source |
Kido M, Yamanaka K, Mitani T, Niki H, Ogura T, Hiraga S. RNase E polypeptides lacking a carboxyl-terminal half suppress a mukB mutation in Escherichia coli. J Bacteriol. 1996 Jul178(13):3917-25. & Bakshi S, Siryaporn A, Goulian M, Weisshaar JC. Superresolution imaging of ribosomes and RNA polymerase in live Escherichia coli cells. Mol Microbiol. 2012 Jul85(1):21-38. doi: 10.1111/j.1365-2958.2012.08081.x.PubMed ID8682798, 22624875
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| Comments |
"In quantitative terms, where does RNase E invest its enzymatic turnovers? This can be estimated with the following assumptions. In a culture of Escherichia coli K12 that grows with a doubling time of about 30 minutes, there will be approximately 50,000 ribosomes [BNID 111527], 375,000 tRNAs [BNID 108611] (7.5 per ribosome) and perhaps a single to at most ten copies of each of the ~2,000 mRNAs per cell. Each mRNA is assumed to be transcribed 5–10 times per
generation (BNID 111529)(thus, ~30,000 mRNA transcripts per generation, assuming that there are three
copies of each mRNA and these are each transcribed five times per generation). To a first
approximation, RNase E must make 150,000 cleavages in rRNA precursors, 248,000 cleavages in tRNA precursors and up to 90,000 cleavages in mRNAs (assuming three per mRNA) during every generation [BNID 111530]. This workload, 16,000 cleavage events per minute [BNID 111531], is fully consistent with an estimate of about 1,470 copies of RNase E per cell (32% of the RNA polymerase content [primary sources]) and a turnover of 11 cleavage events per RNase E per minute (REF. 42 determined with an artificial substrate at 30 °C)." p.53 left column 2nd paragraph:"…at least as abundant as RNase E when expressed from its native promoter (that is, approximately 1,500 molecules per cell, or ~1.5 µM)..." |