Plant Peroxisome Biogenesis: Acquisition/Function of Membrane Proteins

9728935 T释放真核细胞含有膜封闭的隔室(细胞器)，在这些隔室中执行各种细胞功能。这种物理边界内各种功能的隔离对细胞的寿命至关重要：它允许细胞单独调节每个隔室的功能；它防止每个隔室的内容物与其他隔室的内容物相互干扰。然而，它确实要求细胞具有将单个蛋白质分类和转移到其适当的亚细胞位置的机制。细胞内隔室的一种类型是过氧化体，它几乎存在于所有真核细胞中。根据细胞或组织类型的不同，过氧化物酶体参与了一系列非常广泛的代谢途径。本项目的总体目标是了解油菜幼苗中过氧化物体膜蛋白(PMPs)选择性地整合到过氧化物体(乙氧基体)膜上的复杂途径，并了解这些PMPs在油菜幼苗发育过程中在膜内的功能。与植物过氧化体的生物发生有关的三个具体目标被提出。第一个目的是发现可能的膜过氧化体靶向信号(MPTS)，负责将过氧化体抗坏血酸过氧化物酶(PAPX)靶向到乙氧基体，并确定蛋白质在膜内的拓扑方向。这一信息对于油籽乙氧基团尤其相关，对于了解膜如何受到丰富的活性氧物种的保护以及理解将储藏油转化为碳水化合物所需的NAD+再生途径具有特别重要的意义。第二个目的是验证一种假设，即73kodalton的膜结合多肽PMP73是一种新的“过氧素”，它在细胞膜上作为分子伴侣从细胞质中摄取蛋白质。第三个目的是尝试利用先前制备的多克隆兔抗血清来发现更多的植物PM Ps，并已成功地用于发现PMP73和PAPX。很可能，除了了解过氧化物体的生物发生和在油菜种子幼苗发育中的作用这一总体目标外，这些研究的结果还将提供对适用于不同物种和组织的过氧化物体生物发生的更广泛的洞察。

9728935 Trelease Eukaryotic cells contain membrane-enclosed compartments (organelles) in which various cellular functions are carried out. This isolation of various functions within physical boundaries is critical to the life of the cell: it allows the cell to regulate the functions of each compartment separately; and it prevents the contents of each compartment from interfering with others. However, it does require that the cells have mechanisms for sorting and translocating individual proteins to their proper subcellular locations. One type of intracellular compartment is the peroxisome, which occurs in virtually all eukaryotic cells. Peroxisomes participate in a very wide range of metabolic pathways, depending on the cell or tissue type in which they function. The overall goal of this project is to understand the complicated means by which peroxisomal membrane proteins (PMPs) become selectively integrated into the boundary membrane of peroxisomes (glyoxysomes) in oilseed seedlings, and to understand the functions of such PMPs within the membrane as the seedlings develop. Three specific objectives are proposed relative to the biogenesis of plant peroxisomes. The first aim is to discover the putative membrane peroxisomal targeting signal (mPTS) responsible for targeting peroxisomal ascorbate peroxidase (pAPX) to glyoxysomes, and define the topographic orientation of the protein within the membrane. This information is particularly relevant for oilseed glyoxysomes, to understand how the membrane is protected from abundant reactive oxygen species and to understand the pathway for regeneration of NAD+ required for conversion of storage oils into carbohydrates. The second aim is to test the hypothesis that a 73 kilodalton membrane-bound polypeptide, PMP73, is a novel "peroxin" which functions at the boundary membrane as a molecular chaperone in the uptake of proteins from the cytosol. The third aim is to try to discover additional plant PM Ps, using polyclonal rabbit antisera raised previously and already used successfully to discover PMP73 and pAPX. It is likely that, in addition to the overall goal of understanding peroxisomal biogenesis and function in developing oilseed seedlings, the results of these studies will provide more general insight into peroxisomal biogenesis that will be applicable to diverse species and tissues.