Nl. Golitsina et al., CA2-DEPENDENT BINDING OF CALCYCLIN TO MUSCLE TROPOMYOSIN(), Biochemical and biophysical research communications, 220(2), 1996, pp. 360-365
The interaction of calcyclin with tropomyosin and tropomyosin actin wa
s studied with fluorescence titrations and photo-reactive crosslinking
experiments. Titrations of pyreneiodoacetamide-labeled tropomyosin al
one or with actin showed binding of calcyclin to tropomyosin with mu M
dissociation constants when Ca2+ was present. UV irradiation of mixtu
res of calcyclin and gizzard beta beta-tropomyocin labeled with benzop
henone-iodoacetamide at Cys36, with or without actin, produced crossli
nks between tropomyosin chains and calcyclin monomers only in the pres
ence of Ca2+. These data provide direct evidence for a Ca2+-dependent
tropomyosin-calcyclin interaction at or near Cys36 of tropomyosin and
indicate that calcyclin binding to tropomyosin-actin does not cause tr
opomyosin dissociation. (C) 1996 Academic Press, Inc.