The plastid transcription kinase from mustard (Sinapis alba L.). 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 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.
Ogrzewalla
Karsten
K
Plant Cell Physiology & Molecular Biology and Plant Physiology, University of Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany.
Piotrowski
Markus
M
Reinbothe
Steffen
S
Link
Gerhard
G
D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D047390:Casein Kinase II; D002736:Chloroplasts / Q000201:enzymology; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D009149:Mustard Plant / Q000201:enzymology* / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry; D012318:RNA Polymerase I / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D009687:Nuclear Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D012318:RNA Polymerase I