Directed inactivation of the psbI gene does not affect photosystem II in the cyanobacterium Synechocystis sp. PCC 6803.
PsbI is a small, integral membrane protein component of photosystem II (PSII), a pigment-protein complex in cyanobacteria, algae and higher plants. To understand the function of this protein, we have isolated the psbI gene from the unicellular cyanobacterium Synechocystis sp. PCC 6803 and determined its nucleotide sequence. Using an antibiotic-resistance cartridge to disrupt and replace the psbI gene, we have created mutants of Synechocystis 6803 that lack the PsbI protein. Analysis of these mutants revealed that absence of the PsbI protein results in a 25-30% loss of PSII activity. However, other PSII polypeptides are present in near wild-type amounts, indicating that no significant destabilization of the PSII complex has occurred. These results contrast with recently reported data indicating that PsbI-deficient mutants of the eukaryotic alga Chlamydomonas reinhardtii are highly light-sensitive and have a significantly lower (80-90%) titer of the PSII complex. In Synechocystis 6803, PsbI-deficient cells appear to be slightly more photosensitive than wild-type cells, suggesting that this protein, while not essential for PSII biogenesis or function, plays a role in the optimization of PSII activity.
Solar Energy Group, Institute for Physical and Chemical Studies (RIKEN), Wako, Japan.
M
M
Ikeuchi
V K
VK
Shukla
H B
HB
Pakrasi
Y
Y
Inoue
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D017353:Gene Deletion; D005798:Genes, Bacterial; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010788:Photosynthesis / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics*; D045332:Photosystem II Protein Complex; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic
D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C065040:PsbI protein, cyanobacteria