Delayed dissociation of in vitro moving actin filaments from heavy meromyosin induced by low concentrations of Triton X-100.
The in vitro motility of fluorescent actin filaments over heavy meromyosin (HMM) was studied in the presence of the nonionic detergent Triton X-100. Below 0.004% Triton X-100 concentration, motility was not affected. Above 0.007%, motility was not observed because actin filaments were dissociated from HMM. In the Triton X-100 concentration range of 0.004-0.007%, the sliding actin filaments dissociated from HMM with a delay. The dissociation delay time decreased with increasing Triton X-100 concentration, increasing ATP (adenosine-5'-triphosphate) concentration, and increasing temperature. The delayed acto-HMM dissociation was absent when weak-binding kinetic intermediates of the myosin ATPase cycle (M.ATP and M.ADP-Pi) were used. The presence of sliding movement was necessary to evoke the delayed acto-HMM dissociation. The acto-HMM dissociation delay was independent of actin filament length. For a given Triton X-100 concentration, the dissociation delay time was found to be inversely proportional to sliding velocity, indicating that actin filaments travel a more or less constant distance prior to dissociation from HMM. The actin-activated HMM ATPase activity was not inhibited by Triton X-100; rather, it was slightly enhanced. The results imply the presence of a motility-associated conformational change in acto-HMM.
Kellermayer
M S
MS
Central Laboratory, University Medical School of Pécs, Hungary. keller@wsu.edu
D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D007700:Kinetics; D018995:Myosin Heavy Chains / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology*
D000199:Actins; D000255:Adenosine Triphosphate; D017830:Octoxynol; D018995:Myosin Heavy Chains; D009218:Myosins