Partial purification of a spinach thylakoid protein kinase that can phosphorylate light-harvesting chlorophyll a/b proteins
Protein phosphorylation in plant tissues is particularly marked in chloroplasts, protein kinase activity being associated with the outer envelope, the soluble stromal fraction, and the thylakoid membrane. Furthermore, thylakoid-bound activity probably includes several distinct kinases, as suggested by studies of divalent cation specificity and thermal lability carried out with intact thylakoids and by subfractionation of solubilized membranes. Illumination of thylakoids, particularly with red light, promotes the rapid and extensive phosphorylation of the light-harvesting chlorophyll a/b complex (LHCII) on a threonine residue near the amino terminus of the protein. This phosphorylation is thought to be involved in regulating the distribution of absorbed quanta between photosystems II and I and is modulated by the redox state of the thylakoid plastoquinone pool. Neither of the thylakoid kinases reported to date was capable of phosphorylating purified LHCII in vitro or of incorporating phosphate into threonyl residues of exogenous substrates, that some LHCII phosphorylation was catalyzed by a preliminary fraction led workers to suggest that at least one other kinase remained to be isolated. Here, the authors report the solubilization and partial purification of a protein kinase from spinach thylakoids that is capable of phosphorylating LHCII in vitro, and they show that the specific site of phosphorylation is very nearly the same as, if not identical with, the site phosphorylated in organello.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- OSTI ID:
- 5882351
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
PHOSPHOTRANSFERASES
ENZYME ACTIVITY
PURIFICATION
PROTEINS
PHOSPHORYLATION
CHLOROPHYLL
SPINACH
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
ENZYMES
FOOD
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHORUS-GROUP TRANSFERASES
PHYTOCHROMES
PIGMENTS
PLANTS
PORPHYRINS
TRANSFERASES
VEGETABLES
550200* - Biochemistry