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Abstract

The CP29 subunit of Photosystem II is reversibly phosphorylated in Zea mays upon exposure to high light in the cold (Bergantino et al., J Biol Chem 270 (1995) 8474-8481). This phenomenon was previously proposed to be restricted to C4 plants. We present the complete sequence of the CP29 protein, deduced from a maize Lhcb4 cDNA clone, and its comparison with the previously known Lhcb4 sequences of two C3 plants: Hordeum vulgare and Arabidopsis thaliana. Despite the relatively low degree of homology in their amino-terminal region, i.e. the part of the molecule which is phosphorylated in maize, the three polypeptides conserve consensus sequences for the site of phosphorylation. We proved by immunoblotting and 33P-labelling that the same post-translational modification occurs in barley. Being thus common to C3 and C4 plant species, the phosphorylation of this minor antenna complex of Photosystem II appears now as a widespread phenomenon, possibly part of the phosphorylation cascade which signals the redox status of the plastoquinone to the nuclear transcription apparatus. Arabidopsis plants do not show phosphorylation of CP29 in the same conditions, but other low-molecular-weight phosphoproteins, whose role need to be elucidated, become evident.

Light- and pH-dependent structural changes in the PsbS subunit of photosystem II

“…AY104328) were limited to the putative N-terminal chloroplast transit peptide and consisted of the absence of the first seven amino acids (MAAQSML) and the insertion of an alanine residue at position 35. The former difference may be attributed to premature termination of reverse transcription during preparation of the cDNA library (22) and the latter either to a naturally occurring polymorphism or an error in EST sequencing and͞or clustering of overlapping sequences.…”

“…Total DNA from a -Zap II cDNA library of Zea mays (22) was amplified by PCR with synthetic oligonucleotides 5Ј-GTNGARGAYGGNAT HT T YGG-3Ј (forward) and 5Ј-TCRTCNGTDATRAAYTTNCC-3Ј (reverse), designed on conserved amino acid sequences VEDGIFG and GKFITDE. Based on the sequence of the resulting major band, specific nested oligonucleotides 5Ј-ACCTGGAGACGGGCATC-3Ј (forward) and 5Ј-TTGGTGAACCCGAACAGC-3Ј (reverse) were synthesized and further used in separate PCR amplifications with universal primers T7 (reverse) and T3 (forward).…”

A single point mutation (E166Q) prevents dicyclohexylcarbodiimide binding to the photosystem II subunit CP29

“…It could well be conceived that in stress conditions the two effects (phosphorylation and protonation) interact with each other. The result [16]; numbers in the lower left refer to the sequence position in CP29 according to Bergantino and Bassi [32]. Thin arrows, DCCD binding sites in CP26 according to Walters and Horton [40]; arrowhead, DCCD binding site in CP29; underlined, helices; *, identical residues; •, conservative substitution.…”

“…rCP29 and E166Q mutant The apoproteins purified from E.coli carrying either the construct pQBH22 or pQBH22E166Q coding for CP29 respectively with the WT sequence [32] or with the single point mutation E166Q were reconstituted as previously described [17] using a pigment mixture in which Chi a and Chi b were present in a 8:1 ratio.…”

Ultrafast resonance energy transfer from a site-specifically attached fluorescent chromophore reveals the folding of the N-terminal domain of CP29

“…CP29 is the largest of the outer antenna complexes of PSII and it is special because it contains an unusually long N-terminal domain ($100 amino acids). Under cold stress the N-terminus becomes phosphorylated at Thr83 [19] increasing the resistance of the plants to cold stress [20,21]. It was demonstrated that phosphorylation leads to a change in conformation of the protein [22], possibly favoring the dissipative form.…”