Effects of a phosphonic acid analog of adenosine triphosphate on actomyosin systems

Abstract

Adenyl-methylenediphosphonate, a new analog of adenosine triphosphate (ATP), has been studied in actomyosin systems. This analog is structurally identical with ATP except for the replacement of the terminal POP linkage by PCH 2P. It did not replace ATP in causing contraction of glycerinated muscle or a drop in viscosity in actomyosin solutions, and it was not hydrolyzed by a homogenate of glycerinated muscle. A partial inhibition of myofibrillar adenosinetriphosphatase (ATPase) by the analog was observed in the absence of added MgCl 2. This inhibition was not relieved by increasing the ATP concentration; however, it was abolished by the addition of MgCl 2. It was concluded that adenyl-methylenediphosphonate does not interact with the actomyosin sites which react with ATP. It was also concluded that the nature of myofibrillar ATPase is altered by the addition of magnesium ions, and a possible relation between this alteration and the activation of contraction by magnesium ions is suggested.