||Bacteria Escherichia coli
||Ishihama A, Functional modulation of Escherichia coli RNA polymerase. Annu Rev Microbiol. 2000 54: 499-518. DOI: 10.1146/annurev.micro.54.1.499 p.21 figure 2PubMed ID11018136
|| Jishage M, Ishihama A. 1995. Regulation of RNA polymerase sigma subunit synthesis in Escherichia coli: intracellular levels of σ70 and σ38. J. Bacteriol. 177: 6832–35  Jishage M, Iwata A, Ueda S, Ishihama A. 1996. Regulation of RNA polymerase sigma subunit synthesis in Escherichia coli: intracellular levels of four species of sigma subunit under various growth conditions. J. Bacteriol. 178: 5447–51  Maeda H, Jishage M, Nomura T, Fujita N, Ishihama A. Two extracytoplasmic function sigma subunits, sigma(E) and sigma(FecI), of Escherichia coli: promoter selectivity and intracellular levels. J Bacteriol. 2000 Feb182(4):1181-4.PubMed ID7592475, 8808934, 10648550
||Caption to figure 2: "The intracellular concentrations of all seven σ subunits were determined by quantitative Western blot analysis (primary sources), while the dissociation constant between the σ subunit and the core enzyme was determined by FPLC gel chromatography (Maeda H et al, submitted for publication)."
||P.501 bottom paragraph: "The core-binding affinities have been determined in vitro by measuring the amount of core enzyme-bound σ subunit in the presence of various amounts of each σ subunit and a fixed amount of core enzyme (H Maeda, N Fujita, A Ishihama submitted for publication). Among the seven σ subunits from E. coli, σ70 was found to have the highest affinity to the core enzyme. The affinities of the other six σ subunits ranged downwards by 16-fold from σ70 (0.26 nM) to σS, which has the weakest binding activity (4.28 nM) (Figure 2, see color insert). From these two lines of experimental data, [investigators] can now estimate the intracellular concentration of each holoenzyme. The numbers of each free holoenzyme formed in an E. coli cell during exponential growth are thus calculated to be 550 molecules of Eσ70, 95 molecules of EσF, and 55 molecules of EσN (Figure 2, see color insert)." See note beneath figure. Please note-title of primary source  (but not other details such as authors and page numbers) is different between the reference and PUBMED database