Chemical and immunochemical characteristics of tropomyosins from striated and smooth muscle

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Abstract
1. On electrophoresis in dissociating conditions the tropomyosins isolated from skeletal muscles of mammalian, avian and amphibian species migrated as two components. These were comparable with the α and β subunits of tropomyosin present in rabbit skeletal muscle. 2. The α and β components of all skeletal-muscle tropomyosins contained 1 and 2 residues of cysteine per 34000g respectively. 3. The ratio of the amounts of α and β subunit present in skeletal muscle tropomyosins was characteristic for the muscle type. Muscle consisting of slow red fibres contained a greater proportion of β-tropomyosin than muscles consisting predominantly of white fast fibres. 4. Mammalian and avian cardiac muscle tropomyosins consisted of α-tropomyosin only. 5. Mammalian and avian smooth-muscle tropomyosins differed both chemically and immunologically from striated-muscle tropomyosins. 6. Antibody raised against rabbit skeletal α-tropomyosin was species non-specific, reacting with all other striated muscle α-tropomyosin subunits tested. 7. Antibody raised against rabbit skeletal β-tropomyosin subunit was species-specific.