title: Comparison of the fluorescence and conformational properties of smooth and striated tropomyosin.
abstract: In contrast to previous conformational studies with rabbit skeletal and cardiac tropomyosins, (i) when the cysteine side chains of chicken gizzard tropomyosin were reacted with 5,5'-dithiobis(2-nitrobenzoate), an interchain disulfide cross-link was not produced, (ii) when they were labeled with pyrenylmaleimide , excimer fluorescence was not observed, and (iii) when they were labeled with didansylcystine , a long-lived fluorescence component did not appreciably contribute to the fluorescence decay over a large temperature range including the major unfolding transition. In addition, the temperature dependence of the ellipticity at 222 nm did not reveal a pretransition prior to the main helix unfolding transition. This indicates that gizzard tropomyosin does not exhibit a localized chain-open state in the region of its cysteine residues, analogous to that seen with cardiac and skeletal tropomyosins, nor in any other region of the molecule. As a consequence, these observations suggest that gizzard tropomyosin is more rigid than striated tropomyosin.
mesh_terms: D000818:Animals; D002645:Chickens; D004228:Dithionitrobenzoic Acid; D005895:Gizzard, Avian / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D009132:Muscles / Q000502:physiology*; D009928:Organ Specificity; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014335:Tropomyosin / Q000378:metabolism*
chemical_list: D014335:Tropomyosin; D004228:Dithionitrobenzoic Acid