THE MECHANISM FOR MECHANOCHEMICAL ENERGY TRANSDUCTION IN ACTIN-MYOSININTERACTION REVEALED BY IN-VITRO MOTILITY ASSAY WITH ATP ANALOGS

We investigated in vitro motility of F-actin on heavy meromyosin (HMM) and nucleotide triphosphatase activity of acto-HMM by using ATF analo gues of various nucleotide triphosphates (NTPs) and enzymatically clea ved actins. The sliding velocity did not correlate with the actin acti vated HMM-NTPase activity, but correlated strongly with the reciprocal of NTPase activity of HMM itself, i.e., the cycle time of HMM NTPase. This indicated;hat with ATP the complex of myosin with the product, M . ADP . Pi, at the long lived intermediate state of the rate limiting step would play a key role for efficient mechanochemical energy trans duction during actin-myosin interaction. (C) 1996 Academic Press, Inc.