A calcium and free fatty acid-modulated protein kinase as putative effector of the fusicoccin 14-3-3 receptor.
A protein kinase that is activated by calcium and cis-unsaturated fatty acids has been characterized from oat (Avena sativa L.) root plasma membranes. The kinase phosphorylates a synthetic peptide with a motif (-R-T-L-S-) that can be phosphorylated by both protein kinase C (PKC) and calcium-dependent protein kinase (CDPK)-type kinases. Calphostin C and chelerythrine, two PKC inhibitors, completely inhibited the kinase activity with values of inhibitor concentration for 50% inhibition of 0.7 and 30 microns, respectively. At low Ca2+ concentrations cis-unsaturated fatty acids (linolenic acid, linoleic acid, arachidonic acid, and oleic acid) stimulated the kinase activity almost 10-fold. The two inhibitors of the kinase, calphostin C and chelerythrin, strongly reduced the fusicoccin (FC)-induced H+ extrusion, and the activators of the kinase, the cis-unsaturated fatty acids, prevented [3H]FC binding to the FC 14-3-3 receptor. CDPK antibodies cross-reacted with a 43-kD band in the plasma membrane and in a purified FC receptor fraction. A polypeptide with the same apparent molecular mass was recognized by a synthetic peptide that has a sequence homologous to the annexin-like domain from barely 14-3-3. The possibility of the involvement of a kinase, with properties from both CDPK and PKC, and a phospholipase A2 in the FC Signal transduction pathway is discussed.
van der Hoeven
P C
PC
Faculty of Biology, Department of Molecular and Cellular Biology, Vrije Universiteit Amsterdam, The Netherlands.
Siderius
M
M
Korthout
H A
HA
Drabkin
A V
AV
de Boer
A H
AH
D000595:Amino Acid Sequence; D018554:Avena / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D006027:Glycosides / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D010940:Plant Proteins; D011494:Protein Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000502:physiology*; D013379:Substrate Specificity
D005230:Fatty Acids, Nonesterified; D006027:Glycosides; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C080425:fusicoccin receptor protein, plant; C007808:fusicoccin; D011494:Protein Kinases; D002118:Calcium