Rate of isomerization from closed to open complex (K2) of RNAP and pR promoter

Value 0.01 sec^-1
Organism Bacteriophage Lambda
Reference Hawley DK, McClure WR. In vitro comparison of initiation properties of bacteriophage lambda wild-type PR and x3 mutant promoters. Proc Natl Acad Sci U S A. 1980 Nov77(11):6381-5. Table - link PubMed ID6450417
Method Researchers used the abortive initiation assay to monitor in vitro the lags in the formation of open complexes on the two promoters, wildtype pR and mutant x3, when the reaction was initiated with RNA polymerase. The average time necessary for open complex formation, 'Tau obs' was measured at different RNA polymerase concentrations. These data were analyzed in a way that allowed the equilibrium constant for the initial binding (KI = k1/k-1) to be quantitated separately from the rate of open complex formation (k2). This latter process is referred to as an isomerization because it is not known whether the rate of DNA melting or another rate-determining conformational change was measured. Values for the kinetic constants k2 and kon were obtained from the intercepts (intercept = 1/k2) and the slopes (1/S = k1×k2/k-1=kon) of Fig. 2 (graph of tau observed vs. 1/[RNAP])
Entered by Uri M
ID 105130