Dynamics of Palmitic Acid Complexed with Rat Intestinal Fatty Acid Binding Protein
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- 作者：Lingyang Zhu ; Elizabeth Kurian ; Franklyn G. Prendergast ; and Marvin D. Kemple
- 刊名：Biochemistry
- 出版年：1999
- 出版时间：February 2, 1999
- 年：1999
- 卷：38
- 期：5
- 页码：1554 - 1561
- 全文大小：84K
- 年卷期：v.38,no.5(February 2, 1999)
- ISSN：1520-4995
文摘
Dynamics of palmitic acid (PA), isotopically enriched with 13C at the second, seventh, orterminal methyl position, were investigated by 13C NMR. Relaxation measurements were made on PAbound to recombinant rat intestinal fatty acid binding protein (I-FABP) at pH 5.5 and 23 
C, and, forcomparison, 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., andSzabo, A. (1982) J. Am. Chem. Soc. 104, 4546-4559]. The overall rotational correlation time of the fattyacid·protein complex was 2.5 ± 0.4 ns, which is substantially less than the value expected for the proteinitself (>6 ns). Order parameters (S2), which are a measure of the amplitude of the internal motion ofindividual C-H vectors with respect to the PA molecule, while largest for C-2 and smallest for the methylcarbon, were relatively small (<0.4) in the protein complex. S2 values for given C-H vectors also weresmaller for PA in the MPPC micelles and in methanol than in the protein complex. Correlation timesreflective of the time scale of the internal motion of the C-H vectors were in all cases <60 ps. Theseresults support the view that the fatty acid is not rigidly anchored within the I-FABP binding pocket, butrather has considerable freedom to move within the pocket.
C, and, forcomparison, 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., andSzabo, A. (1982) J. Am. Chem. Soc. 104, 4546-4559]. The overall rotational correlation time of the fattyacid·protein complex was 2.5 ± 0.4 ns, which is substantially less than the value expected for the proteinitself (>6 ns). Order parameters (S2), which are a measure of the amplitude of the internal motion ofindividual C-H vectors with respect to the PA molecule, while largest for C-2 and smallest for the methylcarbon, were relatively small (<0.4) in the protein complex. S2 values for given C-H vectors also weresmaller for PA in the MPPC micelles and in methanol than in the protein complex. Correlation timesreflective of the time scale of the internal motion of the C-H vectors were in all cases <60 ps. Theseresults support the view that the fatty acid is not rigidly anchored within the I-FABP binding pocket, butrather has considerable freedom to move within the pocket.