Measurement of ATP turnover during shortening and lengthening of rabbit psoas myofibrils using a fluorescent ATP analog.
In order to study ATP turnover during shortening and lengthening of rabbit psoas myofibrils, we have used fluorescence microscopy in which the displacement of a fluorescent nucleotide analog, 2'(3')-O-[N-[2-[[Cy3] amido] ethyl] carbamoyl]-adenosine 5' triphosphate (Cy3-EDA-ATP) bound to cross-bridge on flash photolysis of caged ATP was measured [Chaen et al. (1997) Biophys. J. 73, 2033-2042]. In the previous paper, we reported that when a myofibril was imposed to shorten with a constant velocity by a piezo-electric actuator, the nucleotide displacement rate constant initially increased to 0.7 s-1 with increasing shortening velocity and then declined with a further increase in shortening velocity. The rate constant during lengthening measured in the present experiment was found to be not significantly affected. These results suggest that the cross-bridge kinetics show a asymmetrical dependence on the mechanical strain in the cross-bridges, namely, the rate constants are not significantly affected at higher strain during lengthening but depend on the lower strain during shortening.
Chaen
S
S
Department of Physiology, School of Medicine, Teikyo University, Tokyo, Japan.
Shirakawa
I
I
Bagshaw
C R
CR
Sugi
H
H
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000502:physiology*; D000818:Animals; D005456:Fluorescent Dyes; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009210:Myofibrils / Q000502:physiology; D011817:Rabbits
C112962:2'(3')-O-(N-(2-((Cy3)amido)ethyl)carbamoyl)adenosine triphosphate; D005456:Fluorescent Dyes; D000255:Adenosine Triphosphate