title: Interaction of iodoacetamidofluorescein-labelled tropomyosin with deoxyribonuclease I.
abstract: 5-Iodoacetamidofluorescein (IAF) reacted with rabbit cardiac muscle tropomyosin (TM) to yield a highly fluorescent product, IAF-TM. The extent of labelling reached one fluorescein group per TM molecule in solutions at pH 8.5. While fluorescence polarization values for IAF-TM solutions were unaffected by the presence or absence of KCl, addition of pancreatic deoxyribonuclease I (DNase I) resulted in a 10% drop, suggestive of a greater freedom of motion of the fluorescein label in the presence of DNase I. Furthermore, a 15% increase in slopes of Stern-Volmer plots for IAF-TM in the presence of DNase I demonstrated a greater susceptibility of the fluorescein group to dynamic quenching by iodide. These results suggest that interaction between DNase I and TM produces a localized unfolding of the coiled coil near the IAF reactive site on TM.
authors.affiliation: Department of Chemistry, University of British Columbia, Vancouver, Canada.
authors.forename: L D
authors.initials: LD
authors.lastname: Burtnick
authors.forename: M K
authors.initials: MK
authors.lastname: Wong
mesh_terms: D000818:Animals; D003850:Deoxyribonuclease I / Q000378:metabolism*; D005452:Fluoresceins; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D014335:Tropomyosin / Q000378:metabolism*
chemical_list: D005452:Fluoresceins; D014335:Tropomyosin; C015296:5-iodoacetamidofluorescein; D011189:Potassium Chloride; D003850:Deoxyribonuclease I