Backbone and Side Chain Dynamics of Uncomplexed Human Adipocyte and Muscle Fatty Acid-Binding Proteins
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- 作者：Keith L. Constantine ; Mark S. Friedrichs ; Michael Wittekind ; Haris Jamil ; Ching-Hsuen Chu ; Rex A. Parker ; Valentina Goldfarb ; Luciano Mueller ; and Bennett T. Farmer ; II
- 刊名：Biochemistry
- 出版年：1998
- 出版时间：June 2, 1998
- 年：1998
- 卷：37
- 期：22
- 页码：7965 - 7980
- 全文大小：289K
- 年卷期：v.37,no.22(June 2, 1998)
- ISSN：1520-4995
文摘
Adipocyte lipid-binding protein (A-LBP) and muscle fattyacid-binding protein (M-FABP)are members of a family of small (~15 kDa) cytosolic proteins thatare involved in the metabolism offatty acids and other lipid-soluble molecules. Although highlyhomologous (65%) and structurally verysimilar, A-LBP and M-FABP display distinct ligand bindingcharacteristics. Since ligand binding maybe influenced by intrinsic protein dynamical properties, we havecharacterized the backbone and sidechain dynamics of uncomplexed (apo) human A-LBP and M-FABP.Backbone dynamics werecharacterized by measurements of 15NT1 and T2 values and{1H}-15N NOEs. These data wereanalyzedusing model-free spectral density functions and reduced spectraldensity mapping. The dynamics of methyl-containing side chains were charaterized by measurements of2H T1 andT1
relaxation times of13C1H22Hgroups. The 2H relaxation data were analyzed using themodel-free approach. For A-LBP, 15Nrelaxationdata were obtained for 111 residues and 2H relaxation datawere obtained for 42 methyl groups. ForM-FABP, 15N relaxation data were obtained for 111 residuesand 2H relaxation data were obtained for 53methyl groups. The intrinsic flexibilities of these two proteinsare compared, with particular emphasisplaced on binding pocket residues. There are a number of distinctdynamical differences amongcorresponding residues between the two proteins. In particular,many residues display greater backbonepicosecond to nanosecond and/or microsecond to millisecond time scalemobility in A-LBP relative toM-FABP, including F57, K58, and most residues in 
-helix 2 (residues28-35). Variations in the dynamicsof this region may play a role in ligand selectivity. The sidechains lining the fatty acid binding pocketdisplay a wide range of motional restriction in both proteins.Side chains showing distinct dynamicaldifferences between the two proteins include those of residues 20, 29,and 51. This information providesa necessary benchmark for determining dynamical changes induced byligand binding and may ultimatelylead to an enhanced understanding of ligand affinity and selectivityamong fatty acid-binding proteins.
relaxation times of13C1H22Hgroups. The 2H relaxation data were analyzed using themodel-free approach. For A-LBP, 15Nrelaxationdata were obtained for 111 residues and 2H relaxation datawere obtained for 42 methyl groups. ForM-FABP, 15N relaxation data were obtained for 111 residuesand 2H relaxation data were obtained for 53methyl groups. The intrinsic flexibilities of these two proteinsare compared, with particular emphasisplaced on binding pocket residues. There are a number of distinctdynamical differences amongcorresponding residues between the two proteins. In particular,many residues display greater backbonepicosecond to nanosecond and/or microsecond to millisecond time scalemobility in A-LBP relative toM-FABP, including F57, K58, and most residues in -helix 2 (residues28-35). Variations in the dynamicsof this region may play a role in ligand selectivity. The sidechains lining the fatty acid binding pocketdisplay a wide range of motional restriction in both proteins.Side chains showing distinct dynamicaldifferences between the two proteins include those of residues 20, 29,and 51. This information providesa necessary benchmark for determining dynamical changes induced byligand binding and may ultimatelylead to an enhanced understanding of ligand affinity and selectivityamong fatty acid-binding proteins.