Ogrzewalla Karsten, Piotrowski Markus, Reinbothe Steffen, Link Gerhard
Plant Cell Physiology & Molecular Biology and Plant Physiology, University of Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany.
Eur J Biochem. 2002 Jul;269(13):3329-37.
The plastid transcription kinase (PTK), a component of the major RNA polymerase complex from mustard chloroplasts, has been implicated in redox-mediated regulation of plastid gene expression. A cloning strategy to define the PTK gene(s) resulted in the isolation of a full-length cDNA for a protein with overall high homology with the alpha subunit of cytosolic casein kinase (CK2) that contained an N-terminal extension for a putative plastid transit peptide. Using in organello chloroplast import studies, immunodetection and MS, we found that the corresponding protein, termed cpCK2alpha, is targeted to the chloroplast and is associated with the plastid RNA polymerase PEP-A. The bacterially overexpressed protein shows CK2 kinase activity and is subject to glutathione inhibition in the same way as authentic chloroplast PTK. Furthermore, it readily phosphorylates components of the plastid transcription apparatus in vitro with a substrate specificity similar to that of PTK.
质体转录激酶（PTK）是芥菜叶绿体主要RNA聚合酶复合物的一个组成部分，参与质体基因表达的氧化还原介导调控。一种用于确定PTK基因的克隆策略，分离出了一个全长cDNA，其编码的蛋白质与胞质酪蛋白激酶（CK2）的α亚基具有高度同源性，且包含一个用于假定质体转运肽的N端延伸。通过叶绿体体内导入研究、免疫检测和质谱分析，我们发现相应的蛋白质（称为cpCK2α）被靶向运输到叶绿体，并与质体RNA聚合酶PEP-A相关联。细菌中过表达的该蛋白质具有CK2激酶活性，并且与天然叶绿体PTK一样受到谷胱甘肽的抑制。此外，它在体外能够轻易地磷酸化质体转录装置的组成成分，其底物特异性与PTK相似。
