Anderson T A, Levitt D G, Banaszak L J
Department of Biochemistry, University of Minnesota, Minneapolis 55455, USA.
Structure. 1998 Jul 15;6(7):895-909. doi: 10.1016/s0969-2126(98)00091-4.
The conformation and assembly of lipoproteins, protein containing large amounts of noncovalently bound lipid, is poorly understood. Lipoproteins present an unusual challenge as they often contain varying loads of lipid and are not readily crystallized. Lipovitellin is a large crystallizable oocyte protein of approximately 1300 residues that contains about 16% w/w lipid. Lipovitellin contains two large domains that appear to be conserved in both microsomal triglyceride transfer protein and apolipoprotein B-100. To gain insight into the conformation of a lipoprotein and the potential modes of binding of both neutral and phospholipid, the crystal structure of lamprey lipovitellin has been determined.
We report here the refined crystal structure of lipovitellin at 2.8 A resolution. The structure contains 1129 amino acid residues located on five peptide chains, one 40-atom phosphatidylcholine, and one 13-atom hydrocarbon chain. The protein contains a funnel-shaped cavity formed primarily by two beta sheets and lined predominantly by hydrophobic residues.
Using the crystal structure as a template, a model for the bound lipid is proposed. The lipid-binding cavity is formed primarily by a single-thickness beta-sheet structure which is stabilized by bound lipid. This cavity appears to be flexible, allowing lipid to be loaded or unloaded.
脂蛋白是含有大量非共价结合脂质的蛋白质，其构象和组装情况尚不清楚。脂蛋白带来了非同寻常的挑战，因为它们通常含有不同量的脂质，且不易结晶。脂卵黄磷蛋白是一种约1300个残基的可结晶大卵母细胞蛋白，含有约16%（重量/重量）的脂质。脂卵黄磷蛋白包含两个大结构域，在微粒体甘油三酯转移蛋白和载脂蛋白B - 100中似乎都是保守的。为了深入了解脂蛋白的构象以及中性脂质和磷脂的潜在结合模式，已确定了七鳃鳗脂卵黄磷蛋白的晶体结构。
我们在此报告脂卵黄磷蛋白在2.8埃分辨率下的精制晶体结构。该结构包含位于五条肽链上的1129个氨基酸残基、一个40原子的磷脂酰胆碱和一个13原子的烃链。该蛋白质含有一个主要由两个β折叠形成的漏斗形腔，腔内主要排列着疏水残基。
以晶体结构为模板，提出了结合脂质的模型。脂质结合腔主要由单厚度的β折叠结构形成，该结构由结合的脂质稳定。这个腔似乎是灵活的，允许脂质加载或卸载。
