title: Ca2+-dependent binding of calcyclin to muscle tropomyosin.
abstract: The interaction of calcyclin with tropomyosin and tropomyosin-actin was studied with fluorescence titrations and photo-reactive crosslinking experiments. Titrations of pyreneiodoacetamide-labeled tropomyosin alone or with actin showed binding of calcyclin to tropomyosin with muM dissociation constants when Ca2+ was present. UV irradiation of mixtures of calcyclin and gizzard beta beta-tropomyosin labeled with benzophenone-iodoacetamide at Cys36, with or without actin, produced crosslinks between tropomyosin chains and calcyclin monomers only in the presence of Ca2+. These data provide direct evidence for a Ca+2-dependent tropomyosin-calcyclin interaction at or near Cys36 of tropomyosin and indicate that calcyclin binding to tropomyosin-actin does not cause tropomyosin dissociation.
authors.affiliation: Muscle Research Group, Boston Biomedical Research Institute, Massachusetts 02114, USA.
authors.forename: N L
authors.initials: NL
authors.lastname: Golitsina
authors.forename: J
authors.initials: J
authors.lastname: Kordowska
authors.forename: C L
authors.initials: CL
authors.lastname: Wang
authors.forename: S S
authors.initials: SS
authors.lastname: Lehrer
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001577:Benzophenones / Q000737:chemistry; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002645:Chickens; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D005895:Gizzard, Avian; D018482:Muscle, Skeletal / Q000737:chemistry; D009132:Muscles / Q000737:chemistry*; D010777:Photochemistry; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; D013050:Spectrometry, Fluorescence; D014335:Tropomyosin / Q000378:metabolism*
chemical_list: D000199:Actins; D001577:Benzophenones; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D003432:Cross-Linking Reagents; D011994:Recombinant Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C489133:S100A6 protein, Gallus gallus; D014335:Tropomyosin; C049923:benzophenone-4-iodoacetamide