Abstract:
:We have studied the kinetics of N epsilon-fluorescein isothiocyanate-lysine-23 cobra alpha-toxin (FITC-toxin) binding to the membrane-associated acetylcholine receptor from the Torpedo californica electric organ. The fluorescent toxin not only enabled us to monitor the binding reaction continuously but also to examine simultaneously the enhancement of ligand fluorescence and the increase in steady state polarization of fluorescence associated with binding of the alpha-toxin. Over the range of concentrations employed, both parameters yielded identical kinetic constants, suggesting that the enhancement of fluorescence of fluorescein and its immobilization are occurring in the same time frame. Both an initial rate analysis and the integrated rate expression showed association to be a simple, reversible bimolecular process. The apparent second-order association rate constant derived from the integrated rate analysis was constant within a factor of 2 over a 40-fold concentration range (6.7 +/- 1.7 X 10(3) M-1 S-1). The unimolecular dissociation rate constant was found to be 3.3 +/- 0.5 X 10(-5) S-1.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Cheung AT,Johnson DA,Taylor Pdoi
10.1016/S0006-3495(84)84167-3subject
Has Abstractpub_date
1984-02-01 00:00:00pages
447-54issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(84)84167-3journal_volume
45pub_type
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