Directed inactivation of the psb1 gene does not affect photosystem 2 in the cyanobacterium Synechocystis sp. PCC 6803
1995
Ikeuchi, M. | Shukla, V.K. | Pakrasi, H.B. | Inoue, Y. (Institute for Physical and Chemical Studies, RIKEN, Wako, Saitama (Japan). Solar Energy Group)
Psb1 is a small, integral membrane protein component of photosystem 2 (PS2), a pigment-protein complex in cyanobacteria, algae and higher plants. To understand the function of this protein, the psb1 gene was isolated from the unicellular cyanobacterium Synechocystis sp. PCC 6803 and determined its nucleotide sequence. Using an antibiotic-resistance cartridge to disrupt and replace the psb1 gene, mutants of Synechocystis 6803 were created that lack the Psb1 protein. Analysis of these mutants revealed that absence of the Psb1 protein results in a 25-30% loss of PS2 activity. However, other PS2 polypeptides are present in near wild-type amounts, indicating that no significant destabilization of the PS2 complex has occurred. These results contrast with recently reported data indicating that Psb1-deficient mutants of the eukaryotic alga Chlamydomonas reinhardtii are highly light-sensitive and have a significantly lower (80-90%) titer of the PS2 complex. In Synechocystis 6803, Psb1-deficient cells appear to be slightly more photosensitive than wild-type cells, suggesting that this protein, while not essential for PS2 biogenesis or function, plays a role in the optimization of PS2 activity.
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