Kinetics of the "on-off" change in regulatory state of the muscle thin filament.
The excimer fluorescence of pyrene iodoacetamide-labeled tropomyosin bound to actin is a probe of the regulatory state change of the muscle thin filament associated with the cooperative binding of myosin subfragment 1 (S1) (Y. Ishii and S. S. Lehrer, Biochemistry 29, 1160, 1990). In this study, the excimer fluorescence was used to monitor the kinetics of the "on-off" state change due to the ATP-induced dissociation of S1 from actin-tropomyosin. A lag in the fluorescence change indicated that the thin filament was maintained in the "on-state" until more than half of the S1s dissociate. The on-off transition rate was slower than the dissociation of the remaining S1s. These delays in relaxation to the "off-state" may explain some observed kinetic and cooperative effects during tension measurements.
Ishii
Y
Y
Boston Biomedical Research Institute, Massachusetts 02114.
Lehrer
S S
SS
D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D005456:Fluorescent Dyes; D007460:Iodoacetamide; D007700:Kinetics; D009132:Muscles / Q000737:chemistry* / Q000378:metabolism; D015879:Myosin Subfragments / Q000378:metabolism*; D011721:Pyrenes; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D014335:Tropomyosin / Q000737:chemistry / Q000378:metabolism*
D000199:Actins; D005456:Fluorescent Dyes; D015879:Myosin Subfragments; D011721:Pyrenes; D014335:Tropomyosin; D000255:Adenosine Triphosphate; C030984:pyrene; D007460:Iodoacetamide