Interaction between Synthetic ATP Analogues and Actomyosin Systems. IV

TONOMURA YUJI, IMAMURA KIICHI, IKEHARA MORIO, UNO HITOSHI, HARADA FUMIO

The following compounds were synthesized as analogues of ATP: Tubercidin 5'-triphosphate (II), 2', 3'-O-isopropylidene 6-chloro-(9-β-D-ribofuranosyl) purine 5'-triphosphate (III) and 2', 3'-O-isopropylidene-6-mercapto-(9-β-D-ribofuranosyl) purine 5'-triphosphate (IV). The interac-tion of these analogues with actomyosin systems, together with those of P³-methyl-adenosine 5'-triphosphate (I), were investigated.<br> The degrees of decrease in light-scattering of myosin B on the addi-tion of these analogues were similar to that induced by ATP, except in the case of Compound I. The rates of hydrolysis of the analogues by myosin B in 0.6M KCl and 7mM Ca⁺⁺ were in the decreasing order of ATP>IV>II>III_??_I, while the order of hydrolysis in 0.075M KCl and 2mM Mg⁺⁺ was II_??_IV>III>ATP_??_I. Compound I was not hy-drolyzed at all. Compounds II and III induced weak contraction of myofibrils, while Compounds IV and I did not.<br> Our present and previous results together with those of other workers on the interaction between ATP analogues and actomyosin systems were summarized. Analysis of these results has considerably clarified the roles of the three parts of ATP (the base, ribose and triphosphate) in the decrease in light-scattering of myosin B caused by ATP, the hydrolysis of ATP by the myosin-type ATPase reaction and the contraction of myofibrils induced by ATP.

Interaction between Synthetic ATP Analogues and Actomyosin Systems. IV

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