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Rotational dynamics of skeletal muscle troponin C
Upon excitation by 280 nm, the intensity decay of the 2 tyrosine residues (residues 10 and 109) of rabbit skeletal muscle troponin C is resolved into three components. The anisotropy decay in the absence of divalent cation is biphasic with a short correlation time of 0.67 ns and a long correlation t...
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Published in: | The Journal of biological chemistry 1993-07, Vol.268 (20), p.14671-14677 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Upon excitation by 280 nm, the intensity decay of the 2 tyrosine residues (residues 10 and 109) of rabbit skeletal muscle
troponin C is resolved into three components. The anisotropy decay in the absence of divalent cation is biphasic with a short
correlation time of 0.67 ns and a long correlation time of 9.23 ns. The limiting anisotropy is 0.225, considerably lower than
the value expected for immobilized tyrosine. Upon excitation by 290 nm, the anisotropy decay is also biphasic, and the limiting
anisotropy increases to 0.274. The recovery of anisotropy by excitation at a wave-length near the red edge of the tyrosine
absorption spectrum is evidence of fluorescence resonance energy transfer between the two tyrosines. For energy transfer to
occur, the average separation between the 2 tyrosines is unlikely much larger than the Förster distance Ro, congruent to 10
A, and this close proximity of the residues would require a highly distorted dumbbell shape of troponin C in solution. These
results are consistent with a flexible central helix, which either has a segmental flexibility with large amplitude or results
in a spectrum of conformations including those in which the two globular domains are in a very close proximity. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(18)82385-7 |