H. Honda et al., REGULATED CROSS-LINKED ACTIN-FILAMENTS AND THE DECOUPLING BETWEEN THEIR ATPASE ACTIVITY AND SLIDING MOTILITY, Journal of Biochemistry, 121(1), 1997, pp. 47-49
Troponin-tropomyosin complex from skeletal muscles was observed to reg
ulate sliding movement of actin filaments on myosin molecules in a man
ner independent of their ATPase activity. When actin molecules were cr
osslinked with DSS (disuccinimidyl suberate), the myosin ATPase activi
ty in the presence of the modified actin filaments complexed with both
troponin and tropomyosin was only 10% less than that in the case of u
nmodified actin, and the ATPase activation was independent of calcium
ions. In contrast, the sliding velocity of the modified actin filament
s on myosin molecules decreased to zero below pCa 6.5. The present res
ults indicate that troponin-tropomyosin complex regulates contractile
movement of actomyosin systems through direct alternation of a mechano
chemical property of the thin filaments, not through a decrease in the
ATPase activity of the myosin molecules.