Thermal protection of the oxygen-evolving machinery by PsbU, an extrinsic protein of photosystem II, in Synechococcus species PCC 7002.
The evolution of oxygen is the reaction that is the most susceptible to heat in photosynthesis. We showed previously that, in the cyanobacterium Synechococcus sp. PCC 7002, some protein factors located on the thylakoid membranes are involved in the stabilization of this reaction against heat-induced inactivation, and we identified cytochrome C550 as one such factor (Y. Nishiyama, H. Hayashi, T. Watanabe, N. Murata [1994] Plant Physiol 105: 1313-1319). In the present study we purified another protein that appears to be essential for the stabilization of the oxygen-evolving machinery. The purified protein had an apparent molecular mass of 13 kD, and the gene encoding the 13-kD protein was cloned from Synechococcus sp. PCC 7002 and sequenced. The deduced amino acid sequence revealed that the protein was homologous to PsbU, an extrinsic protein of the photosystem II complex, which has been found in thermophilic species of cyanobacteria. Western analysis showed that the level of PsbU in thylakoid membranes was constant, regardless of the growth temperature. Our studies indicate that PsbU, a constituent of the photosystem II complex, protects the oxygen-evolving machinery against heat-induced inactivation.
Nishiyama
Y
Y
Department of Regulation Biology, National Institute for Basic Biology, Okazaki, Japan.
Los
D A
DA
Hayashi
H
H
Murata
N
N
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000502:physiology*; D003574:Cytochrome c Group / Q000378:metabolism; D017931:DNA Primers; D006358:Hot Temperature; D007425:Intracellular Membranes / Q000378:metabolism; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D003574:Cytochrome c Group; D017931:DNA Primers; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C107126:PsbU protein, Synechocystis; D011994:Recombinant Proteins; C031732:cytochrome C-550; D010100:Oxygen