tailieunhanh - Báo cáo Y học: A nuclear-encoded CK2-type chloroplast enzyme with redox-sensitive function

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 a 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 cpCK2a, is targeted to the chloroplast and is associated with the plastid RNA polymerase PEP-A. . | Eur. J. Biochem. 269 3329-3337 2002 FEBS 2002 doi The plastid transcription kinase from mustard Sinapis alba L. A nuclear-encoded CK2-type chloroplast enzyme with redox-sensitive function Karsten Ogrzewalla1 Markus Piotrowski2 Steffen Reinbothe2 and Gerhard Link1 1 Plant Cell Physiology Molecular Biology and 2Plant Physiology University of Bochum Germany 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 a 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 cpCK2a 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. Keywords chloroplast transcription factor phosphorylation control plant nuclear gene protein kinase CK2 redox regulation. Chloroplasts the vital organelles of green plant cells contain the photosynthetic apparatus responsible for most life on earth 1 . In addition and in close physical proximity to the photosynthetic apparatus they have a functional gene expression machinery different from that of the nucleo-cytosolic compartment 2 . It has become increasingly clear that signaling mechanisms exist that connect photosynthetic electron flow with gene expression responses 3-5 . These mechanisms include both phosphorylation dephosphorylation .