Disease relevance of Plastoquinol

• Given the presence of PTOX in cyanobacteria, we suggest that this acronym now stand for plastoquinol terminal oxidase [1].

High impact information on Plastoquinol

• Cooperative regulation of light-harvesting complex II phosphorylation via the plastoquinol and ferredoxin-thioredoxin system in chloroplasts [2].
• In order to determine whether the newly discovered plastid oxidase (PTOX) involved in carotenoid biosynthesis acts as a plastoquinol oxidase in higher plant chloroplasts, the Arabidopsis thaliana PTOX gene (At-PTOX) was expressed in tobacco under the control of a strong constitutive promoter [3].
• Fluorescence induction measurements indicate that this is due to an increased plastoquinol oxidase activity in the mutant, causing the plastoquinone pool to be in a more oxidized state under aerobic dark conditions [4].
• Its operation has been described by the "Q-cycle." This model proposes that electrons are transferred from plastoquinol to plastocyanin (the reductant of P700 in Photosystem I) through, obligatorily in series, the iron-sulfur and the cytochrome f redox centers in the cytochrome b(6)f complex [5].
• From inhibitors effects and electronic requirements of the O(2) uptake process, we conclude that an oxidase catalyzing oxidation of plastoquinol and reduction of oxygen to water is present in thylakoid membranes [6].

Biological context of Plastoquinol

• Photosynthesis study of these mutants revealed an altered photosystem I (PSI) activity together with a decrease in PSI amount confirmed by immunodetection experiments, and leading to an over reduction of the plastoquinol pool [7].
• The data are most consistent with plastoquinol/cyt b(6)f interaction as the sensor initiating a signal transduction cascade resulting in accumulation of the crhR transcript [8].
• Plastoquinol oxidation and proton transfer by the cytochrome b(6) f complex on the lumen side of the chloroplast thylakoid membrane are mediated by high and low potential electron transport chains [9].
• Three features of the kinetics allow us to localize simultaneously inhibition at different sites between photoreaction II and the reducing site of plastoquinol [10].
• Single point mutation in the Rieske iron-sulfur subunit of cytochrome b6/f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis [11].

Anatomical context of Plastoquinol

• Activation/deactivation cycle of redox-controlled thylakoid protein phosphorylation. Role of plastoquinol bound to the reduced cytochrome bf complex [12].
• Scavenging of superoxide generated in photosystem I by plastoquinol and other prenyllipids in thylakoid membranes [13].

Associations of Plastoquinol with other chemical compounds

• Anisotropy measurements of intrinsic fluorescence of prenyllipids reveal much higher mobility of plastoquinol than alpha-tocopherol in model membranes [14].
• The recognition that, in photosynthesis, the plastoquinol oxidizing cytochrome b (6f ) complex resembles the ubiquinol oxidizing cytochrome bc1 complex in respiration is one of the examples of exciting universalization in biological research [15].

Gene context of Plastoquinol

• 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 [16].
• IMMUTANS encodes a protein with strong similarities to the mitochondrial alternative oxidase and hence is likely to be a plastoquinol oxidase [17].
• Antioxidant properties of plastoquinol and other biological prenylquinols in liposomes and solution [18].
• Plastoquinol is oxidized by two parallel pathways, via the cytochrome b (6) f complex and a putative cytochrome bd complex, both of which are active in the light and in the dark [19].
• Cytochrome c is reduced mainly by plastoquinol and not by superoxide in thylakoid membranes at low and medium light intensities: its specific interaction with thylakoid membrane lipids [20].

References