TY - JOUR
T1 - Dynamics of palmitic acid complexed with rat intestinal fatty acid binding protein
AU - Zhu, Lingyang
AU - Kurian, Elizabeth
AU - Prendergast, Franklyn G.
AU - Kemple, Marvin D.
PY - 1999/2/2
Y1 - 1999/2/2
N2 - Dynamics of palmitic acid (PA), isotopically enriched with 13C at the second, seventh, or terminal methyl position, were investigated by 13C NMR. Relaxation measurements were made on PA bound to recombinant rat intestinal fatty acid binding protein (I-FABP) at pH 5.5 and 23 °(Degree Sign)C, and, for comparison, on PA incorporated into 1-palmitoyl-2-hydroxy-sn-glycero-3- phosphocholine (MPPC) micelles, and dissolved in methanol. The 13C relaxation data, T1, and steady-state nuclear Overhauser effect (NOE) obtained at two different magnetic fields were interpreted using the model- free approach [Lipari, G., and Szabo, A. (1982) J. Am. Chem. Soc. 104, 4546- 4559]. The overall rotational correlation time of the fatty acid·protein complex was 2.5 ± 0.4 ns, which is substantially less than the value expected for the protein itself (>6 ns). Order parameters (S2), which are a measure of the amplitude of the internal motion of individual C-H vectors with respect to the PA molecule, while largest for C-2 and smallest for the methyl carbon, were relatively small (<0.4) in the protein complex. S2 values for given C-H vectors also were smaller for PA in the MPPC micelles and in methanol than in the protein complex. Correlation times reflective of the time scale of the internal motion of the C-H vectors were in all cases <60 ps. These results support the view that the fatty acid is not rigidly anchored within the I-FABP binding pocket, but rather has considerable freedom to move within the pocket.
AB - Dynamics of palmitic acid (PA), isotopically enriched with 13C at the second, seventh, or terminal methyl position, were investigated by 13C NMR. Relaxation measurements were made on PA bound to recombinant rat intestinal fatty acid binding protein (I-FABP) at pH 5.5 and 23 °(Degree Sign)C, and, for comparison, on PA incorporated into 1-palmitoyl-2-hydroxy-sn-glycero-3- phosphocholine (MPPC) micelles, and dissolved in methanol. The 13C relaxation data, T1, and steady-state nuclear Overhauser effect (NOE) obtained at two different magnetic fields were interpreted using the model- free approach [Lipari, G., and Szabo, A. (1982) J. Am. Chem. Soc. 104, 4546- 4559]. The overall rotational correlation time of the fatty acid·protein complex was 2.5 ± 0.4 ns, which is substantially less than the value expected for the protein itself (>6 ns). Order parameters (S2), which are a measure of the amplitude of the internal motion of individual C-H vectors with respect to the PA molecule, while largest for C-2 and smallest for the methyl carbon, were relatively small (<0.4) in the protein complex. S2 values for given C-H vectors also were smaller for PA in the MPPC micelles and in methanol than in the protein complex. Correlation times reflective of the time scale of the internal motion of the C-H vectors were in all cases <60 ps. These results support the view that the fatty acid is not rigidly anchored within the I-FABP binding pocket, but rather has considerable freedom to move within the pocket.
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U2 - 10.1021/bi982087v
DO - 10.1021/bi982087v
M3 - Article
C2 - 9931022
AN - SCOPUS:0033514406
SN - 0006-2960
VL - 38
SP - 1554
EP - 1561
JO - Biochemistry
JF - Biochemistry
IS - 5
ER -