The interaction between beef adrenodoxin and horse heart cytochrome c was studied by measuring the fluorescence emission of the single tyrosine at residue 82 of adrenodoxin. Addition of cytochrome c at low ionic strength (5 n m sodium morpholinosulfonate, pH 7.5) decreased the 331 nm fluorescence consistent with the formation of a 1:l adrenodoxin-cytochrome c complex with a dissociation constan...

Yeast glucose-6-phosphate dehydrogenase (G6PDH) in solutions exists as the equilibrium mixture of dimers and tetramers. Only dimers are active. The equation responding to these conditions was used to determine the parameters: the specific activity of dimers and the dissociation equilibrium constant of tetramers. The stability of G6PDH dimers were shown to be maintained due to the conformational...

Facilitators are oligonucleotides capable of affecting hammerhead ribozyme activity by interacting with the substrate at the termini of the ribozyme. Facilitator effects were determined in vitro using a system consisting of a ribozyme with 7 nucleotides in every stem sequence and two substrates with inverted facilitator binding sequences. The effects of 9mer and 12mer RNA as well as DNA facilit...

A basic dye is usually obtained in the form of the salt some of which may be transformed in aqueous solution to free base (the m o u n t depending on the "apparent" dissociation constant of the dye and the pH value), and in the range of pH values generally employed with living cells (approximately between pH 5 and 9.5) both forms of dye must be considered. In this range methylene blue, for exam...

3 H-Spiroperidol, a butyrophenone antipsychotic agent, binds specifically and with high affinity to neuroleptic receptors in the 3 corpus striatum and substantia nigra. Scatchard analysis of Hspiroperidol isotherms in the rat striatum revealed a dissociation constant (KQ) of 30 pM and a total receptor density (Bmax) of 430 fmoles/mg protein. In the substantia nigra, the and Bmax values were 42 ...

Thrombomodulin decreased by 20-30% the Michaelis constant of two tripeptidyl p-nitroanilide substrates of thrombin. Thrombomodulin increased the rate of inactivation of thrombin by two peptidyl chloromethane inhibitors by a similar amount. This effect appeared to be due to a decrease in the dissociation constants of the inhibitors. An improved method for the separation of fibrinopeptides A and ...

We have reinvestigated nucleotide binding to actin in order to resolve conflicts regarding the mechanism of nucleotide dissociation and exchange. We present evidence that supports a mechanism for nucleotide binding to actin in which the tightly bound divalent cation (Ca2+ or Mg2+) directly interacts with the bound nucleotide. The dissociation rates of ATP or ADP from actin are limited by the di...

The binding of 125I-asialoorosomucoid and the isolated rabbit hepatic lectin were studied at 0 degrees C. The steady state binding data were analyzed both by a direct curve-fitting procedure that utilizes nonlinear least squares regression analysis, and by conventional Scatchard plot analysis. Two classes of binding sites, present in approximately equal concentrations, were detected by both ana...

The theoretical basis for analyzing the effects of an allosteric modulator on the response to an agonist is described. The effects of an allosteric modulator on the concentration-response curve to an agonist can be attributed to changes in the observed dissociation constant and intrinsic efficacy of the agonist-receptor complex. Each of these two changes can be represented by a coefficient or f...

Transcription of the Bacillus subtilis dra-nupC-pdp operon is repressed by the DeoR repressor protein. The DeoR repressor with an N-terminal His tag was overproduced with a plasmid under control of a phage T5 promoter in Escherichia coli and was purified to near homogeneity by one affinity chromatography step. Gel filtration experimental results showed that native DeoR has a mass of 280 kDa and...