Tryptophan dynamics of the FK506 binding protein: Time-resolved fluorescence and simulations

Norberto D. Silva, Franklyn G. Prendergast

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20 Scopus citations


The FK506-binding protein (FKBP12) is important in the immunosuppressant action of FK506 and rapamycin. We have investigated Trp side chain dynamics in FKBP12, with and without a bound immunosuppressant, by measuring the Trp time-resolved fluorescence anisotropy decay r(t). The r(t) for W59 in aqueous uncomplexed FKBP12 at 20°C is well described by a single exponential with a recovered initial anisotropy, r(o)/(eff), of 0.192 and an overall rotational correlation time for the protein, φ(p), of 4.7 ns; r(o)/(eff) = 0.214 and φ(p) = 4.2 ns for the FKBP12/FK506 complex. Using an expression for the order parameter squared, namely S2 = r(o)/(eff)/r(o)/(T), where r(o)/(T) is the vitrified steady-state excitation anisotropy, we recovered an S2 of 0.75 for W59 fluorescence in uncomplexed FKBP12 and S2 ≃ 1 in the FKBP12/FK506 complex. Results obtained for the FKBP12/rapamycin complex are similar to those found for the FKBP12/FK506 complex. Minimum perturbation mapping simulations were performed on the free and complexed forms of FKBP12 and the results were generally in agreement with the experimental data.

Original languageEnglish (US)
Pages (from-to)1122-1137
Number of pages16
JournalBiophysical Journal
Issue number3
StatePublished - Mar 1996

ASJC Scopus subject areas

  • Biophysics


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