Schonbaum C P, Lee S, Mahowald A P
Department of Molecular Genetics and Cell Biology, University of Chicago, IL 60637.
Proc Natl Acad Sci U S A. 1995 Feb 28;92(5):1485-9. doi: 10.1073/pnas.92.5.1485.
Sequence comparisons of vitellogenins from a wide range of organisms have identified regions of similarity not only to each other but also to vertebrate apolipoproteins (e.g. apoB-100 and apoE). Furthermore, the chicken vitellogenin receptor, which also binds apolipoproteins receptor (LDLR) superfamily [Bujo, H., Hermann, M., Kaderli, M. O., Jacobsen, L., Sugawara, S., Nimpf, J., Yamamoto, T. & Schneider, W. J. (1994) EMBO J. 13, 5165-5175]. The yolk proteins of higher dipterans are exceptional, however, and instead show similarity to lipoprotein lipases. The molecular characterization of the putative Drosophila melanogaster vitellogenin receptor gene, yolkless (yl), described in this report reveals that the protein it encodes (Yl), is also a member of the LDLR superfamily. The ovary-specific 6.5-kb yl RNA codes for a protein of approximately 210 kDa which contains all three motifs common to the LDLR class of proteins. Within this superfamily, Yl may be related more to the LDLR-related proteins (LRPs), which bind both apolipoproteins and lipoprotein lipases. The similarity of Yl to the other LDLR proteins is restricted to the putative extracellular domain. Most noticeably, the cytoplasmic domain of Yl lacks the typical NPXY sequence which is involved in receptor internalization.
对多种生物的卵黄蛋白原进行序列比较后发现，它们不仅彼此之间存在相似区域，而且与脊椎动物载脂蛋白（如载脂蛋白B - 100和载脂蛋白E）也有相似区域。此外，鸡卵黄蛋白原受体也结合载脂蛋白受体（LDLR）超家族[布约，H.，赫尔曼，M.，卡德利，M. O.，雅各布森，L.，菅原，S.，宁普夫，J.，山本，T. & 施奈德，W. J.（1994年）《欧洲分子生物学组织杂志》13卷，5165 - 5175页]。然而，高等双翅目昆虫的卵黄蛋白却很特别，它们与脂蛋白脂肪酶有相似性。本报告中描述的推定黑腹果蝇卵黄蛋白原受体基因——无卵黄（yl）的分子特征表明，其编码的蛋白质（Yl）也是LDLR超家族的成员。卵巢特异性的6.5千碱基yl RNA编码一种约210千道尔顿的蛋白质，该蛋白质包含LDLR类蛋白质共有的所有三个基序。在这个超家族中，Yl可能与LDLR相关蛋白（LRP）关系更密切，LRP既能结合载脂蛋白，也能结合脂蛋白脂肪酶。Yl与其他LDLR蛋白的相似性仅限于推定的细胞外结构域。最值得注意的是，Yl的细胞质结构域缺乏参与受体内化的典型NPXY序列。
