Document Detail

Light affects the accessibility of the thylakoid light harvesting complex II (LHCII) phosphorylation site to the membrane protein kinase(s).
MedLine Citation:
PMID:  12534285     Owner:  NLM     Status:  MEDLINE    
Redox-controlled, reversible phosphorylation of the thylakoid light harvesting complex II (LHCII) regulates its association with photosystems (PS) I or II and thus, energy distribution between the two photosystems (state transition). Illumination of solubilized LHCII enhances exposure of the phosphorylation site at its N-terminal domain to protein kinase(s) and tryptic cleavage in vitro [Zer et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 8277-8282]. Here we report that short illumination (5-10 min, 15-30 micromol m(-2) s(-1)) enhances the accessibility of LHCII phosphorylation site to kinase(s) activity also in isolated thylakoids. However, prolonged illumination or higher light intensities (30 min, 80-800 micromol m(-2) s(-1)) prevent phosphorylation of LHCII in the isolated membranes as well as in vivo, although redox-dependent protein kinase activity persists in the illuminated thylakoids toward exogenous solubilized LHCII. This phenomenon, ascribed to light-induced inaccessibility of the phosphorylation site to the protein kinase(s), affects in a similar way the accessibility of thylakoid LHCII N-terminal domain to tryptic cleavage. The illumination effect is not redox related, decreases linearly with temperature from 25 to 5 degrees C and may be ascribed to light-induced conformational changes in the complex causing lateral aggregation of dephosphorylated LHCII bound to and/or dissociated from PSII. The later state occurs under conditions allowing turnover of the phospho-LHCII phosphate. The light-induced inaccessibility of LHCII to the membrane-bound protein kinase reverses readily in darkness only if induced under LHCII-phosphate turnover conditions. Thus, phosphorylation prevents irreversible light-induced conformational changes in LHCII allowing lateral migration of the complex and the related state transition process.
Hagit Zer; Martin Vink; Susana Shochat; Reinhold G Herrmann; Bertil Andersson; Itzhak Ohad
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochemistry     Volume:  42     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  2003 Jan 
Date Detail:
Created Date:  2003-01-21     Completed Date:  2003-04-07     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  728-38     Citation Subset:  IM    
Department of Biological Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
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MeSH Terms
Membrane Proteins / chemistry,  metabolism*
Models, Chemical
Peas / enzymology,  metabolism
Peptide Fragments / chemistry,  metabolism
Phosphothreonine / metabolism
Photosynthetic Reaction Center Complex Proteins / chemistry,  metabolism*
Plant Leaves / enzymology,  metabolism
Protein Binding
Protein Conformation
Protein Kinases / chemistry,  metabolism*
Thylakoids / chemistry,  enzymology*,  metabolism
Trypsin / metabolism
Reg. No./Substance:
0/Membrane Proteins; 0/Peptide Fragments; 0/Photosynthetic Reaction Center Complex Proteins; 1114-81-4/Phosphothreonine; EC 2.7.-/Protein Kinases; EC 2.7.1.-/light-harvesting complex II kinase; EC

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