title: Osmotic stress induces rapid activation of a salicylic acid-induced protein kinase and a homolog of protein kinase ASK1 in tobacco cells.
abstract: 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).
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawińskiego 5a, 02-106 Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Mikołajczyk
authors.forename: O S
authors.initials: OS
authors.lastname: Awotunde
authors.forename: G
authors.initials: G
authors.lastname: Muszyńska
authors.forename: D F
authors.initials: DF
authors.lastname: Klessig
authors.forename: G
authors.initials: G
authors.lastname: Dobrowolska
mesh_terms: 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
chemical_list: 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