Osmotic stress induces rapid activation of a salicylic acid-induced protein kinase and a homolog of protein kinase ASK1 in tobacco cells.
In tobacco cells, osmotic stress induced the rapid activation of two protein kinases that phosphorylate myelin basic protein. Immunological studies demonstrated that the 48-kD kinase is the salicylic acid-induced protein kinase (SIPK), a member of the mitogen-activated protein kinase family. SIPK was activated 5 to 10 min after the cells were exposed to osmotic stresses, and its activity persisted for approximately 30 min. In contrast, the 42-kD kinase was activated within 1 min after osmotic stress, and its activity was maintained for approximately 2 hr. Moreover, in addition to myelin basic protein, the 42-kD kinase phosphorylated casein and two transcription factors, c-Jun and ATF-2. This latter enzyme was inactivated by a serine/threonine-specific phosphatase but, unlike SIPK, was not affected by a tyrosine-specific phosphatase. After the 42-kD kinase was purified to apparent homogeneity, tryptic peptide analysis indicated that it is a homolog of Arabidopsis serine/threonine kinase1 (ASK1).
Mikołajczyk
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Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawińskiego 5a, 02-106 Warsaw, Poland.
Awotunde
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OS
Muszyńska
G
G
Klessig
D F
DF
Dobrowolska
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G
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins; D004789:Enzyme Activation; D015151:Immunoblotting; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009997:Osmotic Pressure; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010947:Plants, Toxic; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics
C120363:ASK1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; C106405:SA-induced protein kinase