Kawooya J K, Osir E O, Law J H
J Biol Chem. 1986 Aug 15;261(23):10844-9.
Microvitellogenin belongs to a new class of low molecular weight female-specific proteins in insects. The protein is found in the hemolymph (blood) and egg of the tobacco hornworm, Manduca sexta. The isolation of microvitellogenin has been achieved by a combination of gel permeation, cation-exchange, and adsorption chromatographic steps. Microvitellogenin is synthesized by the fat body and appears in the hemolymph 17 days before adult emergence, or 16 days before the onset of egg development. The protein is sequestered from the hemolymph into the egg where it accumulates to a relatively high concentration. The proteins isolated from the hemolymph and the egg are identical in their molecular weight, amino acid compositions, isoelectric points, circular dichroic spectra, immunological properties, and NH2-terminal amino acid sequence. Thus, microvitellogenin does not seem to undergo any modifications before or after it is sequestered in the egg. In solution, the protein exists in a monomeric form and has a secondary structure composed of approximately 38% alpha-helix, as estimated by CD analysis. The CD spectrum of microvitellogenin is unusual in that it has a strong positive band between 220 and 240 nm that may be due to contributions from the aromatic amino acid residues. Unlike the major egg yolk protein of insects, vitellogenin, microvitellogenin does not contain measurable carbohydrate or lipid, and has no immunological, chemical, or physical similarities to vitellogenin. The amino acid composition of microvitellogenin is low in cysteine, but is rich in aspartate. The sex specificity of the protein and its accumulation in the egg justifies the name microvitellogenin, first given to an analogous protein in the egg of the giant silkmoth, Hyalophora cecropia.
微卵黄原蛋白属于昆虫中一类新的低分子量雌性特异性蛋白质。这种蛋白质存在于烟草天蛾（Manduca sexta）的血淋巴（血液）和卵中。微卵黄原蛋白的分离是通过凝胶渗透、阳离子交换和吸附色谱步骤相结合实现的。微卵黄原蛋白由脂肪体合成，在成虫羽化前17天或卵发育开始前16天出现在血淋巴中。该蛋白质从血淋巴中被隔离到卵中，并在那里积累到相对较高的浓度。从血淋巴和卵中分离出的蛋白质在分子量、氨基酸组成、等电点、圆二色光谱、免疫特性和氨基末端氨基酸序列方面是相同的。因此，微卵黄原蛋白在被隔离到卵之前或之后似乎没有经历任何修饰。在溶液中，该蛋白质以单体形式存在，根据圆二色性分析估计，其二级结构由约38%的α-螺旋组成。微卵黄原蛋白的圆二色光谱不同寻常，因为它在220至240纳米之间有一个强正带，这可能是由于芳香族氨基酸残基的贡献。与昆虫的主要卵黄蛋白卵黄原蛋白不同，微卵黄原蛋白不含可测量的碳水化合物或脂质，并且与卵黄原蛋白在免疫、化学或物理方面没有相似之处。微卵黄原蛋白的氨基酸组成中半胱氨酸含量低，但天冬氨酸含量高。该蛋白质的性别特异性及其在卵中的积累证明了微卵黄原蛋白这个名称的合理性，该名称最初是赋予大蚕蛾（Hyalophora cecropia）卵中一种类似蛋白质的。
