Identification of solvent-exposed regions of an FK-506 analog, ascomycin, bound to FKBP using a paramagnetic probe
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- Petros, A.M., Neri, P. & Fesik, S.W. J Biomol NMR (1992) 2: 11. doi:10.1007/BF02192797
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The solvent-exposed regions of [U-13C]ascomycin when bound to its putative target protein; FKBP, have been identified based on the different proton longitudinal relaxation rates (R1 = 1/T1) measured in the absence and presence of the paramagnetic relaxation reagent, 4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-I-oxy (HyTEMPO). The proton T1s of bound ascomycin were determined using a pulse sequence (T1-HMQC) which consists of a 180° proton pulse and a variable delay (τ) followed by a heteronuclear multiple quantum correlation (HMQC) experiment. The solvent-exposed regions of ascomycin determined by these experiments are compared to NOE data in which ascomycin/FKBP contacts were identified and to the X-ray structure of the FK-506/FKBP complex.