Phosphorylation and nitration levels of photosynthetic proteins are conversely regulated by light stress

Abstract

Using a label-free mass spectrometric approach, we investigated light-induced changes in the distribution of phosphorylated and nitrated proteins within subpopulations of native photosynthetic complexes in the thylakoid membrane of Arabidopsis thaliana leaves adapted to growth light (GL) and subsequently exposed to high light (HL). Eight protein phosphorylation sites were identified in photosystem II (PSII) and the phosphorylation level of seven was regulated by HL as determined based on peak areas from ion chromatograms of phosphorylated and non-phosphorylated peptides. Although the phosphorylation of PSII proteins was reported in the past, we demonstrated for the first time that two minor antenna LHCB4 isoforms are alternately phosphorylated under GL and HL conditions in PSII monomers, dimers and supercomplexes. A role of LHCB4 phosphorylation in state transition and monomerization of PSII under HL conditions is proposed. We determined changes in the nitration level of 23 tyrosine residues in five photosystem I (PSI) and nine PSII proteins and demonstrated for the majority of them a lower nitration level in PSI and PSII complexes and supercomplexes under HL conditions, as compared to GL. In contrast, the nitration level significantly increased in assembled/disassembled PSI and PSII subcomplexes under HL conditions. A possible role of nitration in (1) monomerization of LHCB1-3 trimers under HL conditions (2) binding properties of ferredoxin-NADP+ oxidoreductase to photosystem I, and (3) PSII photodamage and repair cycle, is discussed. Based on these data, we propose that the conversely regulated phosphorylation and nitration levels regulate the stability and turnover of photosynthetic complexes under HL conditions.

Protein tyrosine nitration in higher plants grown under natural and stress conditions

“…Tyrosine nitration can change the function of the protein in several ways: function gain; no effect on function; and inhibition of function, the latter being the most common consequence of tyrosine nitration (Greenacre and Ischiropoulos, 2001; Radi, 2004). On the other hand, tyrosine nitration may influence many signal transduction pathways because this modification prevents phosphorylation of tyrosine and consequently affects one regulatory mechanism (Galetskiy et al, 2011). …”

Posttranslational Modifications of Chloroplast Proteins: An Emerging Field

“…Tyr nitration inhibits the activity of both FNR (Chaki et al, 2011) and chloroplast SUPEROXIDE DISMUTASE3, an important scavenger of superoxide anion (O 2 Moreover, the activities of GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE (GAPDH; LozanoJuste et al, 2011) and b-CARBONIC ANHYDRASE (CA), which are involved in photosynthetic carbon metabolism, were decreased upon Tyr nitration . It has been hypothesized that Tyr nitration may disturb the electron transfer chain, because (1) Tyr nitration of the Tyr-262 in the D1 protein may lead to the release of the secondary electron-accepting plastoquinone of PSII from the binding pocket and (2) the double Tyr nitration of PSI subunit D may disturb the flow of electrons from PSI to FERREDOXIN (Galetskiy et al, 2011b). It has also been shown that numerous proteins in PSII monomers, dimers, and PSII-LHCII supercomplexes possess low levels of phosphorylation and high levels of nitration under standard growth conditions, but under high-light conditions, the situation is reversed (Galetskiy et al, 2011b).…”

“…It has been hypothesized that Tyr nitration may disturb the electron transfer chain, because (1) Tyr nitration of the Tyr-262 in the D1 protein may lead to the release of the secondary electron-accepting plastoquinone of PSII from the binding pocket and (2) the double Tyr nitration of PSI subunit D may disturb the flow of electrons from PSI to FERREDOXIN (Galetskiy et al, 2011b). It has also been shown that numerous proteins in PSII monomers, dimers, and PSII-LHCII supercomplexes possess low levels of phosphorylation and high levels of nitration under standard growth conditions, but under high-light conditions, the situation is reversed (Galetskiy et al, 2011b). Thus, the complex and conversely regulated nitration and phosphorylation events might control the stability, turnover, and reassembly of the PSII core complexes and the LHC antenna upon light stress (Galetskiy et al, 2011b).…”

“…It has also been shown that numerous proteins in PSII monomers, dimers, and PSII-LHCII supercomplexes possess low levels of phosphorylation and high levels of nitration under standard growth conditions, but under high-light conditions, the situation is reversed (Galetskiy et al, 2011b). Thus, the complex and conversely regulated nitration and phosphorylation events might control the stability, turnover, and reassembly of the PSII core complexes and the LHC antenna upon light stress (Galetskiy et al, 2011b).…”

Role of Nitric Oxide in Salt Stress-induced Programmed Cell Death and Defense Mechanisms

“…The authors discussed the importance of these posttranslational modifications in the acclimation to high salinity. In contrast, nitration of specific tyrosine of Dl protein (PSBA) of photosystem II leads to the dissociation of the PS II dimers and PS II-LHCII supercomplexes during high light stress (Galetskiy et al 2011). Carbonic anhydrase in sunflower (Chaki et al 2013); and chloroplastic glycerinaldehyde-3-phosphate dehydrogenase in Arabidopsis (Lozano-Juste et al 2011) were also among the Tyr-nitrated proteins under stressS conditions that showed reduced activity.…”