Three-dimensional structure/function analysis of SCP-2-like2 reveals differences among SCP-2 family members
Three-dimensional structure/function analysis of SCP-2-like2 reveals differences among SCP-2 family members
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DOI：
10.1194/jlr.m700460-jlr200
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发表时间：
2008-03-01
影响因子：
6.5
通讯作者：
Lan, Que
中科院分区：
文献类型：
--
作者：
Dyer, David H.;Wessely, Vilena;Lan, Que
蚊子甾醇载体蛋白-2 （AeSCP-2）和甾醇载体蛋白-2样2 （AeSCP-2L2）是SCP-2蛋白家族的成员，在蚊子生命周期中具有相似的表达谱。为了了解不同的SCP-2蛋白如何运输脂质，以1.7埃的分辨率对AeSCP-2L2的三维晶体结构进行了解析。AeSCP-2L2形成二聚体并结合三种脂肪酸，其中一种脂肪酸位于与其他脂肪酸成直角的内腔位置。这是关于SCP-2蛋白家族中配体结合二聚化蛋白的首次报道，表明该家族与配体的相互作用模式比之前报道的要不同得多。通过体内掺入[H-3]胆固醇和[H-3]棕榈酸，研究了AeSCP-2L2的潜在功能。蚊子细胞中AeSCP-2L2的过度表达会导致游离脂肪酸的摄取增加，而成年雌性蚊子细胞中AeSCP-2L2的敲低则会减少脂肪体中血液中游离脂肪酸的积累。相反，过表达或敲低AeSCP-2L2对胆固醇摄取没有影响。我们的研究结果表明，AeSCP-2L2的主要功能是作为一般的细胞内脂肪酸载体，而不是在胆固醇运输中具有专门的作用。
Mosquito sterol carrier protein-2 (AeSCP-2) and sterol carrier protein-2-like2 (AeSCP-2L2) are members of the SCP-2 protein family with similar expression profiles in the mosquito life cycle. In an effort to understand how lipids can be transported by different SCP-2 proteins, the three-dimensional crystal structure of AeSCP-2L2 was solved at 1.7 angstrom resolution. AeSCP-2L2 forms a dimer and binds three fatty acids, one of which resides in a position within the internal cavity at a right angle to the others. This first report of ligand-bound dimerized protein in the SCP-2 protein family indicates that the family has a much more divergent mode of interaction with ligands than previously reported. The potential function of AeSCP-2L2 was investigated via in vivo incorporation of [H-3]cholesterol and [H-3]palmitic acid. Overexpression of AeSCP-2L2 in mosquito cells leads to an increased uptake of free fatty acid, whereas knockdown of AeSCP-2L2 in adult females decreases the accumulation of free fatty acid in the fat body from a blood meal. In contrast, overexpression or knockdown of AeSCP-2L2 has no effect on cholesterol uptake. Our results suggest that the main function of AeSCP-2L2 is as a general intracellular fatty acid carrier, as opposed to having a dedicated role in cholesterol transport.