T. Tobita et al., MUSCLE-TYPE TROPOMYOSIN OF SEA-URCHIN EGG INCREASES THE ACTIN-BINDINGOF NONMUSCLE-TYPE TROPOMYOSIN, Journal of Biochemistry, 120(5), 1996, pp. 922-928
Tropomyosin isoforms in eggs of several species of sea urchins are cla
ssified into two types, muscle-type and nonmuscle-type, based on their
antigenicities, Their actin-binding abilities were investigated using
muscle-type isoform (32K) and nonmuscle-type isoform (30K), which wer
e purified by the method previously reported and separated by isoelect
ric focusing from eggs of sea urchin, Strongylocentrotus intermedius.
Go-sedimentation assays revealed that 32K could stoichiometrically bin
d to actin filaments independently of the 30K, but 30K alone bound ver
y poorly, The actin-binding of 30K was, however, considerably increase
d in the presence of 32K, and the molar ratio of the bound 30K and 32K
was approximately 1:1. The increase in the actin-binding of 30K is pr
obably caused by the interaction of 30K with 32K in a head-to-tail man
ner, as indicated by the higher specific viscosity of the mixture than
that of 32K alone.