Light affects the accessibility of the thylakoid light harvesting complex II (LHCII) phosphorylation site to the membrane protein kinase(s)
2003 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 42, no 3, 728-738 p.Article in journal (Refereed) Published
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, µmol 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 µmol 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°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.
Place, publisher, year, edition, pages
2003. Vol. 42, no 3, 728-738 p.
IdentifiersURN: urn:nbn:se:liu:diva-46746DOI: 10.1021/bi020451rOAI: oai:DiVA.org:liu-46746DiVA: diva2:267642