Intracellular Transport and Secretion of Proteins in Plants

植物中蛋白质的细胞内运输和分泌

• 批准号: 8718443
• 负责人: Russell Jones
• 金额: $ 26.82万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-04-01 至 1991-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8718443&HistoricalAwards=false
• 关键词: Intracellular; Transport; Secretion; Proteins; Plants

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.***//

这项研究包括旨在了解大麦（Hordeum vulgare L. cv Himalaya）糊粉细胞酶的细胞内运输和分泌的实验。 由于其独特的性质，分离的糊粉原生质体已被用于蛋白质分泌的研究。 从大麦糊粉层分离的原生质体对赤霉酸和钙的反应在性质上与分离的糊粉层相似。 该实验室使用原生质体表明，α-淀粉酶同工酶的低等电点 (低 pI) 基团的前体形式被共价修饰为酶的分泌形式。 这种修饰导致同工酶 pI 降低，但不会显着影响蛋白质的分子量。 迄今为止的结果表明这些同工酶没有被糖基化、磷酸化或硫酸化修饰。 Rather the data indicate a form of posttranslational modification of secreted proteins involving side-chain acylation. 来自 14C! 乙酸盐的放射性标记被特异性地掺入低 pI a-淀粉酶的分泌形式中。 分泌蛋白的前体没有被标记，因此乙酸盐不会通过代谢成氨基酸或糖而掺入α-淀粉酶中。 高pI a-淀粉酶的氨基末端乙酰化也被排除，因为这些蛋白质是末端封闭的。 实验旨在研究α-淀粉酶酰化的精确性质以及这种共价修饰的可能功能。 非洲爪蟾卵母细胞实验也正在进行中，这些实验提供了有关蛋白质酰化在分泌中的作用的信息。 将大分子分泌到细胞外部是高等动植物细胞的基本过程。 当植物种子在发芽过程中储存的食物储备被调动时，这一过程尤其重要。 我们对所涉及酶的细胞内转运的了解并不完整。 这项研究解决了这一知识差距。***//