Disease relevance of psbA2

• UV-B radiation induced exchange of the D1 reaction centre subunits produced from the psbA2 and psbA3 genes in the Cyanobacterium synechocystis sp. PCC 6803 [1].
• Specific binding of PCC 6803 RpoC2 (beta') to E. coli core enzyme and its contribution to efficient psbA2 transcription by RNAP-SigA/D suggest that this subunit could confer an important role on the cyanobactrial RNAP [2].
• The psbA2 gene exhibits light-dependent and rhythmic expression in a unicellular cyanobacterium, Microcystis aeruginosa (Synechocystis) K-81 [3].

High impact information on psbA2

• The silent and divergent psbA1 copy of the psbA gene family was activated by exchanging part of its upstream region with a corresponding fragment of the psbA2 copy [4].
• A region of psbA2 coding for 178 amino acids of the carboxyl-terminal portion of the peptide was subjected to random mutagenesis by low fidelity polymerase chain reaction amplification or by hydroxylamine treatment [5].
• We show that UV-B irradiation increases the level of psbA2 mRNA 2-3-fold and, more dramatically, it induces a 20-30-fold increase in the accumulation of the psbA3 mRNA even at levels of irradiation too low to produce losses of either photosystem II activity or D1 protein [6].
• Mutations of arginine 64 within the putative Ca(2+)-binding lumenal interhelical a-b loop of the photosystem II D1 protein disrupt binding of the manganese stabilizing protein and cytochrome c(550) in Synechocystis sp. PCC6803 [7].
• Impact of mutations within the putative Ca2+-binding lumenal interhelical a-b loop of the photosystem II D1 protein on the kinetics of photoactivation and H2O-oxidation in Synechocystis sp. PCC6803 [8].

Chemical compound and disease context of psbA2

• Histidine residue 252 of the Photosystem II D1 polypeptide is involved in a light-induced cross-linking of the polypeptide with the alpha subunit of cytochrome b-559: study of a site-directed mutant of Synechocystis PCC 6803 [9].

Biological context of psbA2

• Furthermore, our findings indicate that UV-B-induced expression of the psbA2 and psbA3 genes is a defense response against UV-B stress, which is regulated, at least, partially at the level of transcription and does not require active electron transport [6].
• Nucleotide sequence analyses indicated that the psbA2 and psbA3 genes encoded predicted proteins with the same amino acid sequence [10].
• In this mutant, psbA2 carries the Ala251-->Val point mutation, which confers resistance to the photosystem II electron transport inhibitor metribuzin, but psbA3 is the same as in the wild-type [1].
• The 5' region and transcription initiation sites of the psbA-2 and psbA-3 genes of Synechocystis 6803 were determined [11].
• Inactivation of the psbA-2 gene resulted in an eightfold up-regulation of the psbA-3 gene [11].

Associations of psbA2 with chemical compounds

• Reverse transcriptase PCR analysis indicated that the psbA1 gene and the psbA2/psbA3 gene(s) were expressed in photosynthetically grown cells in the presence of atrazine [10].

Regulatory relationships of psbA2

• Expression of the dark-induced lrtA and light-induced psbA2/3 transcript was significantly reduced in the sigB and sigD knockout strains, respectively [12].

Other interactions of psbA2

• In this study, we investigated the effect of UV-B irradiation on the transcription of the psbA2 and psbA3 genes encoding identical D1 proteins [6].
• The light-regulated expression of the activated psbA1 gene showed that the inserted psbA2 segment contains the information necessary for light-dependent as well as high-light-stimulated transcription [4].
• The core enzyme with purified a sigma factor, SigA/SigD or SigB, allowed specific in vitro transcription from the light-inducible psbA2 or the dark-/heat-inducible lrtA/hspA promoters, respectively [2].

Analytical, diagnostic and therapeutic context of psbA2

• Comparative sequence analyses of the mutants identified a hexanucleotide repeat as possible cis element in psbA2 light regulation [13].

References