Intracellular Transport and Secretion of Proteins in Plants

这项研究包括旨在了解 细胞内运输和分泌酶， 大麦（Hordeum vulgare L.）cv Himalaya）。 由于其独特的性质， 原生质体已被用来研究蛋白质 分泌物 大麦原生质体的反应 糊粉质对赤霉酸和钙的转化率为 类似于孤立的糊粉层。 使用 原生质体这个实验室已经表明，前体形式的 低等电点（低pI）α-淀粉酶同工酶群 被共价修饰为酶的分泌形式。 这种修饰导致同工酶pI降低 而不显著影响聚合物的分子量， 蛋白 迄今为止的结果表明，这些同工酶不是 通过糖基化、磷酸化或硫酸化修饰。 相反，数据表明了一种翻译后形式 涉及侧链的分泌蛋白的修饰 酰化反应。 来自<$14C的放射性标记！醋酸盐特别是 掺入低pI α-淀粉酶的分泌形式中。 的 分泌蛋白的前体没有被标记，所以乙酸 不通过其代谢掺入α-淀粉酶中， 氨基酸或糖。 高pI的氨基末端乙酰化 α-淀粉酶也被排除，因为这些蛋白质是末端- 被挡出. 实验旨在研究精确的 α-淀粉酶酰化反应的性质和酶的可能功能 这种共价修饰。 非洲爪蟾卵母细胞实验 提供了蛋白质酰化作用的信息， 分泌也在进行。 大分子向细胞外的分泌是一种 高等动植物细胞的基本过程。 这 这一过程在植物种子储存时尤为重要 食物储备在发芽期间被调动。 我们 有关酶的细胞内转运的知识 不完整 本研究旨在解决这一知识差距。**//

This research includes experiments aimed at understanding the intracellular transport and secretion of enzymes from aleurone cells of barley (Hordeum vulgare L. cv Himalaya). Because of their unique properties, isolated aleurone protoplasts have been exploited for studies of protein secretion. The response of protoplasts isolated from barley aleurone to gibberellic acid and calcium is qualitatively similar to that of isolated aleurone layers. Using protoplasts this lab has shown that precursor forms of the low isoelectric point (low-pI) group of a-amylase isozymes are covalently modified to the secreted forms of the enzyme. This modification results in the lowering of isozyme pI without significantly affecting the molecular weight of the protein. Results to date show that these isozymes are not modified by glycosylation, phosphorylation or sulfation. Rather the data indicate a form of posttranslational modification of secreted proteins involving side-chain acylation. Radiolabel from ı14C!acetate is specifically incorporated into secreted forms of low-pI a-amylase. The precursor of the secreted protein is not labeled, so acetate is not incorporated into a-amylase via its metabolism into amino acids or sugars. Amino-terminal acetylation of high-pI a-amylase is also ruled out since these proteins are end- blocked. Experiments are designed to investigate the precise nature of a-amylase acylation and the possible function of this covalent modification. Experiments with Xenopus oocytes that provide information on the role of protein acylation in secretion are also being conducted. The secretion of macromolecules to the cell exterior is a fundamental process of higher plant and animal cells. This process is particularly important in plant seeds when stored food reserves are mobilized during germination. Our knowledge of intracellular transport of the enzymes involved is incomplete. This research addresses this knowledge gap.***//