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Motion of myosin fragments during actin‐activated ATPase: fluorescence correlation spectroscopy study
Author(s) -
Borejdo Julian
Publication year - 1979
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1979.360181111
Subject(s) - heavy meromyosin , chemistry , myosin , fluorescence , fluorescence correlation spectroscopy , actin , translational motion , atpase , molecule , biophysics , meromyosin , analytical chemistry (journal) , myosin head , biochemistry , chromatography , myosin light chain kinase , enzyme , organic chemistry , physics , classical mechanics , quantum mechanics , biology
The rates of the translational motion of myosin fragments, heavy meromyosin (HMM), and heavy meromyosin subfragment‐1 (HMM S‐1) were measured during actin‐activated ATPase reaction by the method of fluorescence correlation spectroscopy. This technique monitors the random fluctuations in the concentration of fluorescent molecules in an open volume which result from the translational diffusion of the molecular species under observation. The statistical behavior of the fluctuations is represented in the form of the autocorrelation function, which is related to the translational diffusion coefficient of the fluorescent molecules. The translational motion of fluorescently labeled myosin fragments was progressively slowed down after additions of increasing amounts of actin in the presence of excess MgATP. When these results are interpreted according to a simple binding scheme, the extent of the retardation can be used to obtain the apparent association constant for binding of S‐1 and HMM to actin in the presence of MgATP. In 0.1 M KCl and at 23°C, the apparent association constants were determined as K app HMM = 2.2 × 10 4 M −1 and K app S‐1 = 8.8 × 10 3 for HMM and S‐1, respectively.