TY - JOUR
T1 - On the Relation between Effector Concentration and the Rate of Induced Enzyme Synthesis
AU - Yagil, Gad
AU - Yagil, Ezra
N1 - Funding Information:
Supported by a grant to E. Yagil by the B. de Rothschild Foundation for the Advancement of Science in Israel.
PY - 1971
Y1 - 1971
N2 - The Jacob and Monod scheme for the regulation of enzyme formation leads to the following relation between the relative rate of enzyme synthesis α and cellular effector concentration E (the lower sign is for repressible systems): log (α/1 - α - αb) = ± n log [E] + log αb ± log K1. This equation permits linear plotting of experimental data and the evaluation of three quantities: n, the number of effector molecules combining with a repressor molecule, K1, the dissociation constant of this interaction and K2/Rt, the ratio of repressor-operator dissociation constant to total repressor concentration. Measurements on the repression of alkaline phosphatase in Escherichia coli as a function of phosphate concentration are reported and fit the proposed equation with n = 1, indicating that the binding of a single phosphate to the repressor species may be sufficient to cause repression. K1 of this interaction was found to be 0.58 ±0.11 × 10-3 M. The available data regarding the enzymes of the lac operon in a variety of E. coli strains, and several other enzymes are analyzed. It is confirmed that the lac repressor interacts with 2 isopropyl thiogalactoside (IPTG) molecules to relieve repression with a K1 = 50 ±20 × 10-12 M2. In some strains, separate binding constants for the first and second IPTG molecules can be evaluated.
AB - The Jacob and Monod scheme for the regulation of enzyme formation leads to the following relation between the relative rate of enzyme synthesis α and cellular effector concentration E (the lower sign is for repressible systems): log (α/1 - α - αb) = ± n log [E] + log αb ± log K1. This equation permits linear plotting of experimental data and the evaluation of three quantities: n, the number of effector molecules combining with a repressor molecule, K1, the dissociation constant of this interaction and K2/Rt, the ratio of repressor-operator dissociation constant to total repressor concentration. Measurements on the repression of alkaline phosphatase in Escherichia coli as a function of phosphate concentration are reported and fit the proposed equation with n = 1, indicating that the binding of a single phosphate to the repressor species may be sufficient to cause repression. K1 of this interaction was found to be 0.58 ±0.11 × 10-3 M. The available data regarding the enzymes of the lac operon in a variety of E. coli strains, and several other enzymes are analyzed. It is confirmed that the lac repressor interacts with 2 isopropyl thiogalactoside (IPTG) molecules to relieve repression with a K1 = 50 ±20 × 10-12 M2. In some strains, separate binding constants for the first and second IPTG molecules can be evaluated.
UR - http://www.scopus.com/inward/record.url?scp=0014974440&partnerID=8YFLogxK
U2 - 10.1016/S0006-3495(71)86192-1
DO - 10.1016/S0006-3495(71)86192-1
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:0014974440
SN - 0006-3495
VL - 11
SP - 11
EP - 27
JO - Biophysical Journal
JF - Biophysical Journal
IS - 1
ER -