Mutation of residue threonine-2 of the D2 polypeptide and its effect on photosystem II function in Chlamydomonas reinhardtii

Christos Andronis, Olaf Kruse, Z. Deák, I. Vass, Bruce A. Diner, Peter J. Nixon

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Abstract

The D2 polypeptide of the photosystem II (PSII) complex in the green alga Chlamydomonas reinhardtii is thought to be reversibly phosphorylated. By analogy to higher plants, the phosphorylation site is likely to be at residue threonine-2 (Thr-2). We have investigated the role of D2 phosphorylation by constructing two mutants in which residue Thr-2 has been replaced by either alanine or serine. Both mutants grew photoautotrophically at wild-type rates, and noninvasive biophysical measurements, including the decay of chlorophyll fluorescence, the peak temperature of thermoluminescence bands, and rates of oxygen evolution, indicate little perturbation to electron transfer through the PSII complex. The susceptibility of mutant PSII to photoinactivation as measured by the light-induced loss of PSII activity in whole cells in the presence of the protein-synthesis inhibitors chloramphenicol or lincomycin was similar to that of wild type. These results indicate that phosphorylation at Thr-2 is not required for PSII function or for protection from photoinactivation. In control experiments the phosphorylation of D2 in wild-type C. reinhardtii was examined by 32P labeling in vivo and in vitro. No evidence for the phosphorylation of D2 in the wild type could be obtained. [14C]Acetate-labeling experiments in the presence of an inhibitor of cytoplasmic protein synthesis also failed to identify phosphorylated (D2.1) and nonphosphorylated (D2.2) forms of D2 upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Our results suggest that the existence of D2 phosphorylation in C. reinhardtii is still in question.

Original languageEnglish
Pages (from-to)515-524
Number of pages10
JournalPlant Physiology
Volume117
Issue number2
Publication statusPublished - 1998

Fingerprint

Chlamydomonas reinhardtii
Photosystem II Protein Complex
Threonine
threonine
photosystem II
polypeptides
phosphorylation
Phosphorylation
mutation
Peptides
Mutation
Protein Synthesis Inhibitors
mutants
Lincomycin
protein synthesis inhibitors
lincomycin
Chlorophyta
Chloramphenicol
Chlorophyll
chloramphenicol

ASJC Scopus subject areas

  • Plant Science

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Mutation of residue threonine-2 of the D2 polypeptide and its effect on photosystem II function in Chlamydomonas reinhardtii. / Andronis, Christos; Kruse, Olaf; Deák, Z.; Vass, I.; Diner, Bruce A.; Nixon, Peter J.

In: Plant Physiology, Vol. 117, No. 2, 1998, p. 515-524.

Research output: Contribution to journalArticle

Andronis, Christos ; Kruse, Olaf ; Deák, Z. ; Vass, I. ; Diner, Bruce A. ; Nixon, Peter J. / Mutation of residue threonine-2 of the D2 polypeptide and its effect on photosystem II function in Chlamydomonas reinhardtii. In: Plant Physiology. 1998 ; Vol. 117, No. 2. pp. 515-524.
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