||Bacteria Escherichia coli
||X. Sunney Xie, Paul J. Choi, Gene-Wei Li, Nam Ki Lee, and Giuseppe Lia, 'Single-Molecule Approach to Molecular Biology in Living Bacterial Cells', Annu. Rev. Biophys. 2008. 37:p.419PubMed ID18573089
||Gilbert W, Muller-Hill B. 1966. Isolation of the lac repressor. Proc. Natl. Acad. Sci. USA 56:1891–98PubMed ID16591435
||10 molecules of tetrameric lac repressor according to: Benno Muller-hill, 1996, The Lac Operon: A Short History Of A Genetic Paradigm, Publisher: Walter de Gruyter. Berlin. New York. Part 3.2 pp.135, citing the same primary source. 10 molecules per cell also according to Benjamin Lewin Genes VIII 2004 p.295 5th paragraph. See Wang et al., 2013 PMID 23262491 p.174 right column bottom paragraph: "In addition, prior theoretical models demonstrating that the fastest possible searches require both 3D diffusion and 1D sliding assume that the search is being conducted by just one protein molecule [refs 9-11, 15-17]. This assumption is reasonable for low-abundance proteins, such as the lac repressor (fewer than ten molecules per cell) but is less appropriate when considering proteins present at higher concentrations."