Kawooya J K, Osir E O, Law J H
Department of Biochemistry, University of Arizona, Tucson 85721.
J Biol Chem. 1988 Jun 25;263(18):8740-7.
The egg of Manduca sexta contains a very high density lipophorin (VHDLp-E; Mr approximately equal to 4.14 x 10(5), rho = 1.238 g/ml) that is derived from the high density lipophorin (HDLp-A; Mr approximately equal to 7.63 x 10(5), rho = 1.076 g/ml) of the hemolymph. The selective uptake of HDLp-A into the egg and its subsequent conversion to VHDLp-E was studied both in vivo and in vitro. Upon entering the egg, an estimated 530 mol of lipid were stripped from each mol of HDLp-A, and 68% of the diacylglycerol fraction was converted to triacylglycerol. In addition, the two molecules of the low molecular weight apolipoprotein, apolipophorin-III, of HDLp-A were dissociated from the lipophorin particle. The VHDLp-E thus formed consisted of 80% protein and 20% lipid, 75% of which was phospholipid. HDLp-A labeled in vivo with [35S]methionine in its apoprotein moiety was injected into females at the onset of egg development, and its incorporation in a series of follicles at different stages of growth was measured. There was increased accumulation of [35S]HDLp-A in the follicles as they matured. The apoproteins of [35S]HDLp-A were not hydrolyzed when the particle was internalized by the follicle. In the accompanying paper we have presented the evidence that the apoproteins of HDLp-A are retained in the follicles (Kawooya, J.K., and Law, J.H. (1988) J. Biol. Chem. 263, 8748-8753).
烟草天蛾的卵含有一种极高密度脂蛋白（VHDLp-E；相对分子质量约为4.14×10⁵，密度ρ = 1.238 g/ml），它源自血淋巴中的高密度脂蛋白（HDLp-A；相对分子质量约为7.63×10⁵，密度ρ = 1.076 g/ml）。对HDLp-A选择性摄取到卵中及其随后转化为VHDLp-E的过程进行了体内和体外研究。进入卵后，每摩尔HDLp-A估计有530摩尔脂质被去除，并且二酰基甘油部分的68%转化为三酰基甘油。此外，HDLp-A的两分子低分子量载脂蛋白——载脂蛋白-III从脂蛋白颗粒上解离。如此形成的VHDLp-E由80%的蛋白质和20%的脂质组成，其中75%是磷脂。在卵发育开始时，将在体内用[³⁵S]甲硫氨酸标记其载脂蛋白部分的HDLp-A注射到雌性体内，并测量其在不同生长阶段的一系列卵泡中的掺入情况。随着卵泡成熟，[³⁵S]HDLp-A在卵泡中的积累增加。当颗粒被卵泡内化时，[³⁵S]HDLp-A的载脂蛋白不会被水解。在随附的论文中，我们已提供证据表明HDLp-A的载脂蛋白保留在卵泡中（卡沃亚，J.K.，和劳，J.H.（1988年）《生物化学杂志》263，8748 - 8753）。
