INSECT STORAGE PROTEINS

昆虫进化出了一种储存氨基酸的系统，其中的氨基酸 幼虫摄食末期来自饲料蛋白质的酸 被用来合成大量的一些定义明确的蛋白质，称为 储存蛋白质。储存蛋白是六聚体，包含一个或多个 亚基的类型。在Manduca sexta中，这一研究的主题 应用中，有三种主要的存储蛋白(SP)：SP-1或 富含芳香族氨基酸的蛋白质：SP-2，富含 蛋氨酸；以及SP-3，一种尚未确定特征的储存蛋白。在.期间 在最后一个幼虫体育场，这些蛋白质在体内积累到非常高的水平 血液和它们的mrna代表了脂肪体内的主要物种， 关于合成的。在幼虫生命结束时，SP-2和SP-3被带回 脂肪体内，包装成蛋白质颗粒，而SP-1则留在 血。SP-1在两性中的分布相同，而SP-2和SP-3在 在女性血液中的浓度要高得多，而且在血液中出现得更早 末龄雌幼虫多于雄幼虫。这些蛋白质都不是 在成人血淋巴中发现。 这些贮藏蛋白质是两个基本的 细胞生物学中的问题，即：1)荷尔蒙和发育如何 它们的基因表达受到控制；2)贮藏蛋白是如何表达的 被肥胖的身体吸收，这个系统是如何区分 两种储藏蛋白？我们建议使用储存蛋白质来 在烟草角虫Manduca模型系统中研究这些问题 Sexta，通过追求以下具体目标：1)确定 SP-2和SP-3的蛋白质(CDNA)和基因序列；2)调查 贮藏蛋白基因中潜在的顺式调控元件；3) 识别的交易因子的分离和鉴定 贮藏蛋白基因中的顺式调控元件；4)特性 脂肪体内吸收储存蛋白质的能力。

Insects have evolved a system for storage of amino acids in which amino acids derived from dietary proteins during the last feeding larval stage are used to synthesize large amounts of a few well-defined proteins, called storage proteins. Storage proteins are hexamers, containing one or more types of subunits. In Manduca sexta, the subject of study in this application, there are three major storage proteins (SP); SP-1 or arylphorin, a protein rich in aromatic amino acids; SP-2, a protein rich in methionine; and SP-3, an as yet uncharacterized storage protein. During the last larval stadium, these proteins accumulate to very high levels in the blood and their mRNAs represent major species in the fat body, the site of synthesis. At the end of larval life SP-2 and SP-3 are taken back into the fat body and packaged as protein granules, while SP-1 remains in the blood. SP-1 is found equally in both sexes, whereas SP-2 and SP-3 occur in much higher concentrations in female blood and appear earlier in the blood of last instar female larvae than in male larvae. None of these proteins are found in adult hemolymph. THe storage proteins serve as important models for two fundamental questions in cell biology, viz, 1) how is the hormonal and developmental expression of their genes controlled; and 2) how are the storage proteins taken up by the fat body, and how does this system discriminate between the two classes of storage proteins? We propose to use the storage proteins to investigate these questions in a model system, the tobacco hornworm Manduca sexta, through pursuit of the following specific aims: 1) Determination of the protein (cDNA) and gene sequences for sp-2 and sp-3; 2) Investigation of potential cis-regulatory elements in the storage protein genes; 3) Isolation and characterization of transacting factors which recognize cis-regulatory elements in the storage protein genes; 4) Characterization of storage protein uptake up the fat body.