Frolov A, Miller K, Billheimer J T, Cho T H, Schroeder F
Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA.
Lipids. 1997 Nov;32(11):1201-9. doi: 10.1007/s11745-997-0154-5.
Although it was recently recognized that sterol carrier protein-2 (SCP-2) interacts with fatty acids, little is known regarding the specificity of SCP-2 for long-chain fatty acids or branched-chain fatty-acid-like molecules. Likewise the location of the fatty-acid binding site within SCP-2 is unresolved. A fluorescent cis-parinaric acid displacement assay was used to show that SCP-2 optimally interacted with 14-22 carbon chain lipidic molecules: polyunsaturated fatty acids > monounsaturated, saturated > branched-chain isoprenoids > branched-chain phytol-derived fatty acids. In contrast, the other major fatty-acid binding protein in liver, fatty-acid binding protein (L-FABP), displayed a much narrower carbon chain preference in general: polyunsaturated fatty acids > branched-chain phytol-derived fatty acids > 14- and 16-carbon saturated > branched-chain isoprenoids. However, both SCP-2 and L-FABP displayed a very similar unsaturated fatty-acid specificity profile. The presence and location of the SCP-2 lipid binding site were investigated by fluorescence energy transfer. The distance between the SCP-2 Trp50 and bound cis-parinaric acid was determined to be 40 A. Thus, the SCP-2 fatty-acid binding site appeared to be located on the opposite side of the SCP-2 Trp50. These findings not only contribute to our understanding of the SCP-2 ligand binding site but also provide evidence suggesting a potential role for SCP-2 and/or L-FABP in metabolism of branched-chain fatty acids and isoprenoids.
尽管最近人们认识到固醇载体蛋白-2（SCP-2）可与脂肪酸相互作用，但对于SCP-2对长链脂肪酸或类支链脂肪酸分子的特异性了解甚少。同样，SCP-2内脂肪酸结合位点的位置也尚未明确。采用荧光顺式紫黄质酸置换试验表明，SCP-2与含14 - 22个碳原子的链状脂质分子能实现最佳相互作用：多不饱和脂肪酸＞单不饱和脂肪酸、饱和脂肪酸＞支链类异戊二烯＞支链叶绿醇衍生脂肪酸。相比之下，肝脏中的另一种主要脂肪酸结合蛋白，即脂肪酸结合蛋白（L-FABP），总体上表现出更窄的碳链偏好性：多不饱和脂肪酸＞支链叶绿醇衍生脂肪酸＞14碳和16碳饱和脂肪酸＞支链类异戊二烯。然而，SCP-2和L-FABP都表现出非常相似的不饱和脂肪酸特异性谱。通过荧光能量转移研究了SCP-2脂质结合位点的存在和位置。测定出SCP-2的色氨酸50（Trp50）与结合的顺式紫黄质酸之间的距离为40埃。因此，SCP-2脂肪酸结合位点似乎位于SCP-2 Trp50的另一侧。这些发现不仅有助于我们理解SCP-2配体结合位点，还提供了证据，表明SCP-2和/或L-FABP在支链脂肪酸和类异戊二烯的代谢中可能发挥作用。
