title: Tryptophan dynamics of the FK506 binding protein: time-resolved fluorescence and simulations.
abstract: 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 degrees C is well described by a single exponential with a recovered initial anisotropy, r(eff)o, of 0.192 and an overall rotational correlation time for the protein, phi p, of 4.7 ns; r(eff)o = 0.214 and phi p = 4.2 ns for the FKBP12/FK506 complex. Using an expression for the order parameter squared, namely S2 = r(eff)o/rTo, where rTo is the vitrified steady-state excitation anisotropy, we recovered an S2 of 0.75 for W59 fluorescence in uncomplexed FKBP12 and S2 approximately equal to 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.
authors.affiliation: Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905, USA.
authors.forename: N D
authors.initials: ND
authors.lastname: Silva
authors.forename: F G
authors.initials: FG
authors.lastname: Prendergast
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D005454:Fluorescence Polarization; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007166:Immunosuppressive Agents / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D011090:Polyenes / Q000378:metabolism / Q000494:pharmacology; D011487:Protein Conformation; D020123:Sirolimus; D013053:Spectrophotometry; D016559:Tacrolimus / Q000378:metabolism / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D007166:Immunosuppressive Agents; D011090:Polyenes; D014364:Tryptophan; D022021:Tacrolimus Binding Proteins; D020123:Sirolimus; D016559:Tacrolimus