A1 Refereed original research article in a scientific journal
Phosphorylation of light-harvesting complex II and photosystem II core proteins shows different irradiance-dependent regulation in vivo - Application of phosphothreonine antibodies to analysis of thylakoid phosphoproteins
Authors: Rintamaki E, Salonen M, Suoranta UM, Carlberg I, Andersson B, Aro EM
Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Publication year: 1997
Journal: Journal of Biological Chemistry
Journal name in source: JOURNAL OF BIOLOGICAL CHEMISTRY
Journal acronym: J BIOL CHEM
Volume: 272
Issue: 48
First page : 30476
Last page: 30482
Number of pages: 7
ISSN: 0021-9258
DOI: https://doi.org/10.1074/jbc.272.48.30476
Abstract
An immunological approach using a polyclonal phosphothreonine antibody is introduced for the analysis of thylakoid protein phosphorylation in vivo, Virtually the same photosystem II (PSII) core phosphoproteins (D1, D2, CP43, and the psbH gene product) and the light-harvesting chlorophyll a/b complex II (LHCII) phosphopolypeptides (LHCB1 and LHCB2), as earlier identified by radiolabeling experiments, were recognized in both pumpkin and spinach leaves, Notably, the PSII core proteins and LHCII polypeptides were found to have a different phosphorylation pattern in vivo with respect to increasing irradiance. Phosphorylation of the PSII core proteins in leaf discs attained the saturation level at the growth light intensity, and this level was also maintained at high irradiances, Maximal phosphorylation of LHCII polypeptides only occurred at low light intensities, far below the growth irradiance, and then drastically decreased at higher irradiances. These observations are at variance with traditional studies in vitro, where LHCII shows a light-dependent increase in phosphorylation, which is maintained even at high irradiances, Only a slow restoration of the phosphorylation capacity for LHCII polypeptides at the low light conditions occurred in vivo after the high light-induced inactivation, Furthermore, if thylakoid membranes were isolated from the high light-inactivated leaves, no restoration of LHCII phosphorylation took place in vitro, However, both the high light-induced inactivation and low light-induced restoration of LHCII phosphorylation seen in vivo could be mimicked in isolated thylakoid membranes by incubating with reduced and oxidized diothiothreitol, respectively, We propose that stromal components are involved in the regulation of LHCII phosphorylation in vivo, and inhibition of LHCII phosphorylation under increasing irradiance results from reduction of the thiol groups in the LHCII kinase.
An immunological approach using a polyclonal phosphothreonine antibody is introduced for the analysis of thylakoid protein phosphorylation in vivo, Virtually the same photosystem II (PSII) core phosphoproteins (D1, D2, CP43, and the psbH gene product) and the light-harvesting chlorophyll a/b complex II (LHCII) phosphopolypeptides (LHCB1 and LHCB2), as earlier identified by radiolabeling experiments, were recognized in both pumpkin and spinach leaves, Notably, the PSII core proteins and LHCII polypeptides were found to have a different phosphorylation pattern in vivo with respect to increasing irradiance. Phosphorylation of the PSII core proteins in leaf discs attained the saturation level at the growth light intensity, and this level was also maintained at high irradiances, Maximal phosphorylation of LHCII polypeptides only occurred at low light intensities, far below the growth irradiance, and then drastically decreased at higher irradiances. These observations are at variance with traditional studies in vitro, where LHCII shows a light-dependent increase in phosphorylation, which is maintained even at high irradiances, Only a slow restoration of the phosphorylation capacity for LHCII polypeptides at the low light conditions occurred in vivo after the high light-induced inactivation, Furthermore, if thylakoid membranes were isolated from the high light-inactivated leaves, no restoration of LHCII phosphorylation took place in vitro, However, both the high light-induced inactivation and low light-induced restoration of LHCII phosphorylation seen in vivo could be mimicked in isolated thylakoid membranes by incubating with reduced and oxidized diothiothreitol, respectively, We propose that stromal components are involved in the regulation of LHCII phosphorylation in vivo, and inhibition of LHCII phosphorylation under increasing irradiance results from reduction of the thiol groups in the LHCII kinase.
UTU Research Portal