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

Citation
E. Rintamaki et al., 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, The Journal of biological chemistry, 272(48), 1997, pp. 30476-30482
Citations number
35
ISSN journal
00219258
Volume
272
Issue
48
Year of publication
1997
Pages
30476 - 30482
Database
ISI
SICI code
0021-9258(1997)272:48<30476:POLCAP>2.0.ZU;2-6
Abstract
An immunological approach using a polyclonal phosphothreonine antibody is introduced for the analysis of thylakoid protein phosphorylation i n vivo, Virtually the same photosystem II (PSII) core phosphoproteins (D1, D2, CP43, and the psbH gene product) and the light-harvesting chl orophyll a/b complex II (LHCII) phosphopolypeptides (LHCB1 and LHCB2), as earlier identified by radiolabeling experiments, were recognized i n both pumpkin and spinach leaves, Notably, the PSII core proteins and LHCII polypeptides were found to have a different phosphorylation pat tern 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 hig h irradiances, Maximal phosphorylation of LHCII polypeptides only occu rred at low light intensities, far below the growth irradiance, and th en drastically decreased at higher irradiances. These observations are at variance with traditional studies in vitro, where LHCII shows a li ght-dependent increase in phosphorylation, which is maintained even at high irradiances, Only a slow restoration of the phosphorylation capa city for LHCII polypeptides at the low light conditions occurred in vi vo after the high light-induced inactivation, Furthermore, if thylakoi d membranes were isolated from the high light-inactivated leaves, no r estoration 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 t hylakoid membranes by incubating with reduced and oxidized diothiothre itol, respectively, We propose that stromal components are involved in the regulation of LHCII phosphorylation in vivo, and inhibition of LH CII phosphorylation under increasing irradiance results from reduction of the thiol groups in the LHCII kinase.