Topographical studies on subunit polypeptides of oxygen-evolving PS II preparations by reversible crosslinking.

放氧膜制剂含有几种内在多肽，包括约47和43-40 kDa的两种携带叶绿素的亚基多肽，涉及水氧化的33、24和18 kDa的三种外在蛋白，以及天线色素复合物，如高等植物中的捕光叶绿素a/B蛋白（LHCP）和蓝藻中的藻胆蛋白。在本研究中，我们通过可逆交联来检测两种放氧制剂的亚基多肽之间的最近邻关系。以最大分子跨度为12的二硫代双（琥珀酰亚胺基丙酸酯）为交联剂，研究了菠菜放氧膜多肽亚基间的最近邻关系<ang>。在与水氧化相关的三种外源蛋白中，发现33 kDa蛋白与光系统II反应中心复合物的47 kDa亚基多肽交联，而18和24 kDa蛋白相互交联。33 kDa蛋白与47 kDa蛋白的结合表明后者在水氧化中起重要作用.聚球藻放氧颗粒中保留少量别藻蓝蛋白的多肽之间的最近邻关系也进行了研究。交联和随后的交联产物的二硫键的裂解表明，在77 K下发射长波长荧光带的别藻蓝蛋白种类与颗粒交联。二维SDS聚丙烯酰胺凝胶电泳显示，藻胆蛋白是专门与叶绿素携带40 kDa的蛋白质的光系统II反应中心复合物交联。结果表明，40 kDa的脱辅基蛋白在激发能量从藻胆体到光系统II反应中心的转移中起着关键作用。

Oxygen-evolving membrane preparations contain several intrinsic polypeptides including two chlorophyll-carrying subunit polypeptides of about 47 and 43-40 kDa, three extrinsic proteins of 33, 24 and 18 kDa involving in water oxidation and antenna pigment complexes such as light-harvesting chlorophyll a/b proteins (LHCP) in higher plants and phycobiliproteins in cyanobacteria. In this study, we examined the nearest neighbor relationships among subunit polypeptides of two oxygen-evolving preparations by reversible crosslinking.1. The nearest neighbor relationships among subunit polypeptides of spinach oxygen-evolving membrane were studied with a cleavable bifunctional crosslinking reagent, dithiobis(succinimidyl propionate) with a maximum molecular span of 12 <ang> . Of the three extrinsic proteins which are associated with water oxidation, the 33 kDa protein was found to crosslink with the 47 kDa subunit polypeptide of the photosystem II reaction center complex, whereas the 18 and 24 kDa proteins crosslinked with each other. The association of the 33 kDa protein with the 47 kDa protein suggests that the latter protein plays an important role in water oxidation.2. The nearest neighbor relationships among polypeptides of synechococcus oxygen-evolving particles which retains a small amount of allophycocyanin were also examined. Crosslinking and subsequent cleaving of disulfide bonds of the crosslinked product showed that an allophycocyanin species which emits a long wavelength fluorescence band at 77K is crosslinked with the particles. Two-dimensional SDS polyacrylamide gel electrophoresis revealed that the phycobiliprotein is specifically crosslinked with a chlorophyll-carrying 40 kDa protein of the photosystem II reaction center complex. The results suggest that the 40 kDa apoprotein plays a key role in the excitation energy transfer from phycobilisomes to the photosystem II reaction center.