title: Role of tropomyosin in the regulation of contraction in smooth muscle.
abstract: Smooth muscle contraction is due to the interaction ofmyosin filaments with thin filaments. Thin filaments are composed of actin, tropomyosin, caldesmon and calmodulin in ratios 14:2:1:1. Tissue specific isoforms of act and beta tropomyosin are expressed in smooth muscle. Compared with skeletal muscle tropomyosin, the cooperative activation of actomyosin is enhanced by smooth muscle tropomyosin: cooperative unit size is 10 and the equilibrium between on and off states is shifted towards the on state. The smooth muscle-specific actin-bindingprotein caldesmon, together with calmodulin regulates the activity of the thin filament in response to Ca2+. Caldesmon and calmodulin control the tropomyosin-mediated transition between on and offactivity states.
authors.affiliation: National Heart and Lung Institute, Imperial College London, Dovehouse St., London SW3 6LY, UK. s.marston@imperial.ac.uk
authors.forename: Steve
authors.initials: S
authors.lastname: Marston
authors.forename: M
authors.initials: M
authors.lastname: El-Mezgueldi
mesh_terms: D000199:Actins / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry; D002148:Calmodulin-Binding Proteins / Q000737:chemistry; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism*; D011487:Protein Conformation; D020033:Protein Isoforms; D014335:Tropomyosin / Q000737:chemistry* / Q000502:physiology*
chemical_list: D000199:Actins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D020033:Protein Isoforms; D014335:Tropomyosin; D002118:Calcium