Content of acetylase and β-galactosidase subunits of the lac operon

Range ~8,500 acetylase subunits/cell: ~75,000 β-galactosidase subunits/cell subunits/cell
Organism Bacteria Escherichia coli
Reference Fox CF, Carter JR, Kennedy EP. Genetic control of the membrane protein component of the lactose transport system of Escherichia coli. Proc Natl Acad Sci U S A. 1967 Mar57(3):698-705. p.704 top paragraphPubMed ID16591520
Comments P.704 top paragraph: "From the point of view of the mechanism of synthesis of proteins of the lac operon it is of interest to compare the number of subunits of this protein with those of β-galactosidase and acetylase. Zabin [ref 21] reports that the acetylase constitutes about 0.15 per cent of the total protein of ML 308 when grown at 37˚ with good aeration. The basic subunit is thought to be of mol wt 35,000. Assuming that 1 mg of total cellular protein represents about 3×10^9 cells, it may be calculated that each cell contains about 8,500 acetylase subunits. A similar calculation can be made for the number of β-galactosidase subunits. Assuming that β-galactosidase makes up 5 per cent of the total protein of ML 308, and that the enzyme is made up of subunits of mol wt 135,000, then each cell contains about 75,000 such units."
Entered by Uri M
ID 112551