Journal Article

Absence of the PsbZ Subunit Prevents Association of PsbK and Ycf12 with the PSII Complex in the Thermophilic Cyanobacterium <i>Thermosynechococcus elongatus</i> BP-1

Masako Iwai, Takehiro Suzuki, Naoshi Dohmae, Yasunori Inoue and Masahiko Ikeuchi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 12, pages 1758-1763
Published in print December 2007 | ISSN: 0032-0781
Published online December 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm148
Absence of the PsbZ Subunit Prevents Association of PsbK and Ycf12 with the PSII Complex in the Thermophilic Cyanobacterium Thermosynechococcus elongatus BP-1

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PsbZ (Ycf9) is a membrane protein of PSII complexes and is highly conserved from cyanobacteria to plants. We deleted the psbZ gene in the thermophilic cyanobacterium, Thermosynechococcus elongatus. The mutant cells showed photoautotrophic growth indistinguishable from that of the wild type under low and standard light conditions, while they showed even better growth than the wild type under high light. The mutant accumulated less carotenoids and more phycobiliproteins than the wild type under high light, suggestive of tolerance to photoinhibition. The mutant cells evolved oxygen at a rate comparable with the wild type, while the PSII complex isolated from the mutant retained much lower activity than the wild type. N-terminal sequencing revealed that Ycf12 and PsbK proteins were almost lost in the PSII complex. These results indicate that PsbZ is involved in functional integrity of the PSII complex by stabilizing PsbK and Ycf12. We suggest that Ycf12 is an unidentified membrane-spanning polypeptide that is placed near PsbZ and PsbK in the crystal structure of PSII.

Keywords: PSII; PsbK; PsbZ; Thermosynechococcus elongatus; Ycf9; Ycf12

Journal Article.  3579 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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