Motile activity of actin filaments containing acto-S1dc chimera protein with ATP hydrolysis

Yuuta Uematsu (1), Taro Q.P. Uyeda (2) and Kuniyuki Hatori Kuniyuki (1)

(1) Department of Bio-system Engineering, Yamagata University,
(2) National Institute of Advanced Industrial Science and Technology


Under a fluorescent microscope we researched on properties of acto-S1dc that is a chimera protein composed of actin and myosin motor domain. Acto-S1dc monomers could be polymerized into the filaments with rhodamine-phalloidin and their filaments had a tendency to aggregate. It was found that the aggregated filaments have a weaker affinity for external myosin molecules fixed on glass surface. When the polymerization was done below 0.2 uM of acto-S1dc, this aggregation was somewhat reduced. Although single acto-S1dc filaments were bound to external myosin molecules, they exhibited no siding movement in the presence of ATP. On the other hand, the copolymer filaments that consisted of intact actin monomers and acto-S1dc ones at various molar ratios exhibited the sliding movement. Average velocities of copolymer filaments below 50 % of mixing ratio were almost comparable to that of intact actin filaments. Histogram plotting the frequency of velocity showed that there were faster copolymer filaments compared with intact filaments. In addition, fluorescence intensity of rhodamine-phalloidin-bound acto-S1dc filaments was decreased to 79 % by the addition of 2 mM of ATP, as indicating that structural modulation of the filament might be induced by internal ATP hydrolysis in acto-S1dc constituents.