Structure and Function of the Oxygen Evolving Complex of Photosystem II

从光系统II(PSII)中去除一些调节蛋白得到一种含有七个蛋白质亚基的制剂，该蛋白质亚基能够光诱导放氧活性。同时，这些纯化程序改变了PSII中的放氧和电子转移的性质。这些实验将确定电子转移活性变化的根源。在提纯过程中，将对PSII中的色素和质酚的含量进行定量研究。去除一个28 kDa的叶绿素结合蛋白可以诱导对除草剂敏感的苯醌的光还原；将检测该蛋白的性质以将其置于其他已知的叶绿素结合蛋白的背景下，并确定其在除草剂结合和苯醌光还原调节中的作用。更多的研究将评估几种PSII相关蛋白在为外源多肽提供结合位点方面的作用，并试图确定与PSII结合的低分子量肽是否是活性的基本成分。%光系统II(PSII)催化光驱动的4电子氧化水生成分子氧。使用相对简单的生化程序可以将PSII从叶绿体的类囊体膜中分离出来。在这些膜片上应用非离子洗涤剂可以分离出更简单的制剂，这些制剂含有数量减少的多肽，但同时保持放氧活性。从PSII中去除各种多肽会导致电子转移活性的变化，这些变化的修复已被证明有助于发现放氧反应的新辅助因子。这项研究将推断一组精选的多肽的作用，这些多肽在从PSII中移除时会引起电子转移活性的变化。还将确定与PSII制剂相关的低分子多肽是否在电子转移活性中发挥重要作用。

Removal of a number of regulatory proteins from photosystem II (PSII) results in a preparation containing seven protein subunits which is capable of light-induced oxygen evolution activity. At the same time, these purification routines alter the properties of oxygen evolution and electron transfer in PSII. These experiments will determine the origins of the changes in electron transfer activity. Studies will be conducted to quantify the contents of pigments and plastoquinone in PSII during purification. Removal of a 28 kDa chlorophyll-binding protein can be shown to induce alterations to herbicide-sensitive photoreduction of quinones; the properties of this protein will be examined to place it in the context of other known chlorophyll binding proteins as well as to determine its role in regulation of herbicide binding and quinone photoreduction. Additional investigations will assess the roles of several PSII-associated proteins in providing sites for the binding of extrinsic polypeptides and attempts will be made to determine whether low molecular weight peptides which copurify with PSII are essential components of activity.%%% Photosystem II (PSII) catalyzes the light-driven 4-electron oxidation of water to molecular oxygen. The use of relatively simple biochemical procedures permit the isolation of PSII from thylakoid membranes of chloroplasts. Application of non-ionic detergents to these membrane sheets permits the isolation of simpler preparations which contain reduced numbers of polypeptides, but which at the same time retain oxygen evolution activity. Removal of various polypeptides from PSII induces alterations to electron transfer activity, and the repair of these alterations has proven useful in discovering new cofactors for the oxygen evolving reaction. This research will deduce the roles of a selected set of largely uncharacterized polypeptides which, upon removal from PSII, induce changes to electron transfer activity. It will also be determined whether low molecular weight polypeptides associated with PSII preparations play significant roles in electron transfer activity.***