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, 34 (49), 16039-45

Adenosine 5'-(gamma-thiotriphosphate): An ATP Analog That Should Be Used With Caution in Muscle Contraction Studies

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Adenosine 5'-(gamma-thiotriphosphate): An ATP Analog That Should Be Used With Caution in Muscle Contraction Studies

A M Resetar et al. Biochemistry.

Abstract

The slowly hydrolyzed ATP analog adenosine 5'-(gamma-thiotriphosphate) (ATP gamma S) has been used in many studies of the muscle motor protein myosin in order to form a stable "weak binding" state analogous to the actin-S1-ATP complex However, the results from studies using ATP gamma S do not always agree with the results of experiments using ATP. The binding of myosin subfragment-1-ATP gamma S to actin has now been studied in some detail to determine its relationship to the actin-S1-ATP state. The binding of myosin subfragment-1-ATP gamma S to actin-troponin-tropomyosin is similar in affinity to the binding of myosin subfragment-1-ATP. Like myosin subfragment-1-ATP, the binding is not Ca(2+)-dependent, and most importantly, myosin subfragment-1-ATP gamma S does not stabilize the active configuration of actin-troponin-tropomyosin. Thus, myosin subfragment-1-ATP gamma S is an analog of myosin subfragment-1-ATP but must be used with caution for two reasons: (1) The binding of ATP gamma S to regulated actomyosin subfragment-1 is Ca(2+)-sensitive, and errors can be made in the interpretation of results if proteins are not fully saturated with nucleotide and a mixture of weak and strong binding states is present. (2) At the high concentrations of myosin subfragment-1 used in some experiments, significant amounts of ADP may form.(ABSTRACT TRUNCATED AT 250 WORDS)

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