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Interaction of iodoacetamidofluorescein‐labelled tropomyosin with deoxyribonuclease I
Author(s) -
Burtnick L.D.,
Wong M.K.C.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80554-x
Subject(s) - deoxyribonuclease , chemistry , deoxyribonuclease i , quenching (fluorescence) , fluorescein , fluorescence , tropomyosin , biophysics , fluorescence anisotropy , actin , biochemistry , dna , biology , optics , physics , membrane , base sequence
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.