Number of β-galactosidase per uninduced lac+ cell

Range 10 to 20 Molecules/cell
Organism Bacteria Escherichia coli
Reference Erlich HA, Cohen SN, McDevitt HO. A sensitive radioimmunoassay for detecting products translated from cloned DNA fragments. Cell. 1978 Apr13(4):681-9. doi:10.1016/0092-8674(78)90218-0 p.686 right column 2nd paragraphPubMed ID418881
Primary Source Miller, J. H. (1972). Experiments in Molecular Genetics (New York: Cold Spring Harbor Laboratory). p.398 experiment 57 'Purification of ß-galactosidase', 1st paragraph
Method "Uninduced lac+ cultures, estimated to contain 10-20 ß-galactosidase molecules per cell (primary source) are detected easily and reliably when the lysate from 5×10^7 cells is assayed. When cultured in the presence of IPTG, 1lac+ in 10^3 lac? cells, or as few as 5×10^4 lac+ cells, can be identified."
Comments From primary source: 'In an uninduced lac+ E. coli cell, lac repressor prevents the transcription of lac messenger` hence a basal level of only 10 to 20 molecules of ß-galactosidase is present.' [10 to 20 is the number of lac repressors per cell]
Entered by Uri M
ID 106200