Lemaux P G, Grossman A R
EMBO J. 1985 Aug;4(8):1911-9. doi: 10.1002/j.1460-2075.1985.tb03870.x.
By sequence analysis of previously identified fragments and low stringency hybridization of an identified gene for a phycobiliprotein subunit to total plastid DNA, we have identified four phycobiliprotein subunit genes in a eukaryotic alga, Cyanophora paradoxa. The four phycobiliprotein subunits, alpha and beta of phycocyanin (PC) and allophycocyanin (APC), comprise the bulk of the light-harvesting complex in this alga. The alpha and beta subunit genes encoding each phycobiliprotein (the products of which are required in a 1:1 ratio in the light-harvesting complex) are contiguous; however, the genes for different phycobiliproteins, PC and APC, are located in different regions of the genome. The two PC subunit genes are in the small single copy region of the plastid genome whereas the APC subunit genes are in the large single copy region and the two sets of phycobiliprotein genes are transcribed from opposite strands. The alpha and beta subunits of both PC and APC are encoded in dicistronic transcripts and this arrangement may provide a mechanism by which the two subunits can be synthesized in equimolar amounts. Levels of the PC transcript are approximately five times that of the APC transcript which may reflect the relative abundance of their gene products in the phycobilisome. The 5' ends of the transcripts for PC and APC were mapped and the regulatory regions identified. Several features of the promoter regions for these highly transcribed genes are described.
通过对先前鉴定的片段进行序列分析，以及将已鉴定的藻胆蛋白亚基基因与总质体DNA进行低严谨度杂交，我们在真核藻类蓝氏拟甲色球藻（Cyanophora paradoxa）中鉴定出了四个藻胆蛋白亚基基因。这四个藻胆蛋白亚基，即藻蓝蛋白（PC）和别藻蓝蛋白（APC）的α和β亚基，构成了该藻类光捕获复合物的主要部分。编码每个藻胆蛋白的α和β亚基基因（在光捕获复合物中其产物按1:1比例需要）是相邻的；然而，不同藻胆蛋白PC和APC的基因位于基因组的不同区域。两个PC亚基基因位于质体基因组的小单拷贝区域，而APC亚基基因位于大单拷贝区域，并且两组藻胆蛋白基因从相反的链转录。PC和APC的α和β亚基均由双顺反子转录本编码，这种排列可能提供了一种机制，通过该机制两个亚基可以等摩尔量合成。PC转录本的水平约为APC转录本的五倍，这可能反映了它们的基因产物在藻胆体中的相对丰度。绘制了PC和APC转录本的5'末端图谱并鉴定了调控区域。描述了这些高转录基因启动子区域的几个特征。
