Open AccessNMR 15 N relaxation of the insulin‐like growth factor (IGF)‐binding domain of IGF binding protein‐5 (IGFBP‐5) determined free in solution and in complex with IGF‐II
Author(s) -
Renner Christian,
Holak Tad A.
Publication year - 2001
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2001.01965.x
Subject(s) - insulin like growth factor , insulin like growth factor binding protein , chemistry , growth factor , anisotropy , isotropy , relaxation (psychology) , biochemistry , physics , biology , receptor , optics , neuroscience
15 N NMR relaxation rates of mini‐IGFBP‐5, an N‐terminal insulin‐like growth factor binding domain of the insulin‐like growth factor binding protein 5 (IGFBP‐5), were analysed at three field strengths using the Lipari–Szabo procedure (see below) and reduced spectral density methods. Isotropic and anisotropic Lipari–Szabo models were analysed and an analytical formula for the overall correlation time for anisotropic molecules is presented. Mini‐IGFBP‐5 was found to be mainly rigid on fast ps time scales except for 11 unstructured flexible residues at the C‐terminus. The insulin‐like growth factor binding loop in the apo‐protein exhibits small amounts of flexibility on fast time scales (ps to ns) but several loop residues show significant exchange broadening. These loop residues display no exchange broadening in the complex of IGF‐II/mini‐IGFBP‐5. The isotropic overall tumbling time in solution at 31 °C of mini‐IGFBP‐5 complexed to IGF‐II is τ c = 18.4 ± 0.2 ns indicating a strong tendency for aggregation.