Das Gupta J, Li Q S, Thomson A B, Hunt A G
Department of Agronomy, University of Kentucky, Lexington 40546-0091, USA.
Plant Mol Biol. 1998 Jul;37(4):729-34. doi: 10.1023/a:1006000213403.
We have isolated cDNA clones encoding a novel factor (PAP-I) that is a component of a multi-subunit poly(A) polymerase from pea seedlings. The encoded protein, when isolated from appropriately engineered Escherichia coli, was active as a poly(A) polymerase, either with an associated RNA binding cofactor (PAP-III) or with free poly(A) as an RNA substrate. The latter observation indicates that PAP-I is in fact a poly(A) polymerase. PAP-I bore a striking resemblance to an as yet uncharacterized cyanobacterial protein. This observation suggested a possible chloroplast localization for PAP-I. This hypothesis was tested and found to be substantiated; immunoblot analysis identified PAP-I in chloroplast but not nuclear extracts. Our results suggest that PAP-I is a component of the machinery that adds poly(A) to chloroplast RNAs.
我们已经分离出编码一种新因子（PAP-I）的cDNA克隆，该因子是豌豆幼苗多亚基聚腺苷酸聚合酶的一个组成部分。从经过适当工程改造的大肠杆菌中分离出的编码蛋白，作为聚腺苷酸聚合酶具有活性，无论是与相关的RNA结合辅因子（PAP-III）一起，还是以游离聚腺苷酸作为RNA底物。后一观察结果表明PAP-I实际上是一种聚腺苷酸聚合酶。PAP-I与一种尚未鉴定的蓝细菌蛋白有惊人的相似之处。这一观察结果提示PAP-I可能定位于叶绿体。该假设经过测试并得到证实；免疫印迹分析在叶绿体提取物中鉴定出了PAP-I，但在核提取物中未鉴定出。我们的结果表明，PAP-I是向叶绿体RNA添加聚腺苷酸的机制的一个组成部分。
