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Lack of the D2 protein in a Chlamydomonas reinhardtii psb D mutant affects photosystem II stability and D1 expression
Author(s) -
Erickson Jeanne M.,
Rahire Michéle,
Malnoë Pia,
GirardBascou Jacqueline,
Pierre Yves,
Bennoun Pierre,
Rochaix JeanDavid
Publication year - 1986
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1986.tb04422.x
Subject(s) - marie curie , biology , chlamydomonas reinhardtii , humanities , mutant , genetics , gene , philosophy , european union , business , economic policy
D1 and D2, two chloroplast proteins with apparent mol. wt of 32 000‐34 000, play an important role in the photosynthetic reactions mediated by the membrane‐bound protein complex of photosystem II (PSII). We have isolated and characterized an uniparental, non‐photosynthetic mutant of Chlamydomonas reinhardtii and show that the mutation is in the chloroplast gene psb D, coding for D2. A 46 bp direct DNA duplication in the coding region of the mutant gene causes a frame‐shift which results in a psb D transcript coding for 186 amino acid residues instead of the normal 352. The truncated D2 peptide is never seen, even after pulse‐labeling, suggesting that the mutant protein is very unstable. In addition, little or no D1 protein is detected in this mutant although the gene and normal levels of mRNA for D1 are present in mutant cells. All other core PSII proteins are synthesized and inserted into the membrane fraction, but never accumulate. These results suggest that D2 contributes not only to the stabilization of the PSII complex in the membrane, but also may play a specific role in the regulation of the D1 protein, either at the translational or post‐translational level.