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会得到含有7个蛋白亚基的制备，这些蛋白亚基具有光诱导析氧活性。同时，这些纯化程序改变了PSII的析氧和电子转移性质。这些实验将确定电子转移活性变化的起源。在纯化过程中，将对PSII中色素和质体醌的含量进行定量研究。去除28kda的叶绿素结合蛋白可以诱导醌类除草剂敏感光还原的改变；我们将研究这种蛋白质的特性，以便将其与其他已知的叶绿素结合蛋白进行比较，并确定其在调节除草剂结合和醌光还原中的作用。进一步的研究将评估几种PSII相关蛋白在提供外源性多肽结合位点方面的作用，并试图确定与PSII共聚合的低分子量肽是否是活性的必要组成部分。光系统II （PSII）催化光驱动的4电子氧化水为分子氧。使用相对简单的生化程序可以从叶绿体类囊体膜中分离PSII。将非离子洗涤剂应用于这些膜片，可以分离出更简单的制剂，这些制剂含有较少数量的多肽，但同时保持出氧活性。从PSII中去除各种多肽会引起电子转移活性的改变，而这些改变的修复已被证明有助于发现新的助氧反应的辅因子。本研究将推断出一组选择的大部分未表征的多肽的作用，这些多肽在从PSII中去除后，会诱导电子转移活性的变化。还将确定与PSII制剂相关的低分子量多肽是否在电子传递活性中起重要作用

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.***