Disease relevance of petB

• Cytochrome b6 arginine 214 of Synechococcus sp. PCC 7002, a key residue for quinone-reductase site function and turnover of the cytochrome bf complex [1].

High impact information on petB

• To this end, we have constructed three deletion mutant strains, each lacking one of the major chloroplast pet genes: the delta petA, delta petB and delta petD strains were unable to synthesize cyt f, cyt b6 and subunit IV (suIV) respectively [2].
• As an approach to the study of the biogenesis of the cytochrome b6/f complex, we characterized the behaviour of its constitutive subunits in mutant strains of Chlamydomonas reinhardtii bearing well-defined mutations [2].
• The assembly of cytochrome b6/f complexes: an approach using genetic transformation of the green alga Chlamydomonas reinhardtii [2].
• The chloroplast petD gene encodes subunit IV of the cytochrome b6/f complex and is required for photosynthetic electron transport [3].
• Lateral redistribution of cytochrome b6/f complexes along thylakoid membranes upon state transitions [4].

Biological context of petB

• Nucleotide sequence of the frxC, petB and trnL genes in the chloroplast genome of Chlamydomonas reinhardtii [5].
• We previously reported that these mutants fail to accumulate the chloroplast petD mRNA and its product, subunit IV of the cytochrome b6/f complex, which is essential for photosynthesis [6].
• These results are discussed in light of the translational autoregulation model that has been proposed for cytochrome b6/f complex assembly in Chlamydomonas [7].
• Evidence for a selective destabilization of an integral membrane protein, the cytochrome b6/f complex, during gametogenesis in Chlamydomonas reinhardtii [8].
• Molecular genetic identification of a pathway for heme binding to cytochrome b6 [9].

Anatomical context of petB

• The amounts of petB- and petD-containing mRNAs were reduced in the mutants compared to wild-type plants, but the remaining mRNA was normally associated with polysomes [7].
• Thylakoids of N-limited cells have reduced amounts of cytochrome b6, cytochrome f, and light-harvesting complexes [10].
• This 66-kDa polypeptide reacts with antibodies to cytochrome f and accumulates in gametes only in conditions that promote destabilisation of the cytochrome b6/f complex [11].

Associations of petB with chemical compounds

• This gene modification mimics the presence of proline codons at the same position in the petB genes of maize and tobacco, which are subsequently edited to leucine codons at the RNA level [12].
• The loss of cytochrome b6/f complexes during gametogenesis is prevented by the addition of cycloheximide, but is chloramphenicol insensitive [8].
• The light-induced turnover of the D1 protein subunit of reaction center II (RCII) was investigated in Chlamydomonas reinhardtii y-1 (control) and D6, AC208, and B4 mutants lacking cytochrome b6/f, plastocyanin or photosystem I activity, respectively, and, thus, impaired in light-dependent plastoquinol (PQH2) oxidation [13].
• Thin three-dimensional crystals of the cytochrome b6 f complex from the unicellular algae Chlamydomonas reinhardtii have been grown by BioBeads-mediated detergent removal from a mixture of protein and lipid solubilized in Hecameg [14].
• Function-directed mutagenesis of the cytochrome b6f complex in Chlamydomonas reinhardtii: involvement of the cd loop of cytochrome b6 in quinol binding to the Q(o) site [15].

Physical interactions of petB

• Highly purified preparations of cytochrome b6 f complex from the unicellar freshwater alga Chlamydomonas reinhardtii contain about 1 molecule of chlorophyll a/cytochrome f [16].

Other interactions of petB

• At variance with the pet genes in higher plant chloroplasts, the petB and petD genes are continuous, not adjacent and not located next to the psbB gene [17].
• The resulting homoplasmic petG deletion strains are unable to grow photosynthetically, and immunoblot analysis shows markedly decreased levels of cytochrome b6, cytochrome f, the Rieske iron-sulfur protein, and subunit IV [18].
• Biochemical comparison of the proline-containing transformants with a cytochrome b6 mutant deficient in heme-attachment indicates that their primary defect is at the level of assembly of apocytochrome b6 with the bh heme, thereby preventing assembly of the whole cytochrome b6f complex [12].

Analytical, diagnostic and therapeutic context of petB

• The structure of the cytochrome b6 f complex has been investigated by electron microscopy and image analysis of thin three-dimensional crystals [19].
• These mutations resulted in the appearance of distinct immunoreactive species of cytochrome b6, which allowed us to specifically identify cytochrome b6 with altered bh or bl ligation [9].

References