Heterogeneity in photosystem I. Evidence from cation-induced decrease in Photosystem I electron transport

Bose, Salil; Ramanujam, P.

doi:10.1016/0005-2728(84)90138-5

Cited by 5 publications

(3 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The effect of MgZ on isolated PSI particles is, therefore, to directly promote electron transport reactions. It should be noted that the erfect or cations on PSI electron transport in vitro in chloroplasts poisoned with 3-(3',4'-dich1orophenyl)-1 ,Idimethylurea is reported to be light-independent, but inhibitory [37]. The reason for this discrepancy is not known.…”

Section: Resultsmentioning

confidence: 94%

Protein phosphorylation and Mg²⁺influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Harrison

Allen

1992

European Journal of Biochemistry

View full text Add to dashboard Cite

A material containing only photosystem I (PSI) and the chlorophyll-a/b-binding light-harvesting complex of PSII (LHC-11) has been isolated from the chloroplast thylakoid membrane by solubilization with Triton X-100. Fluorescence spectroscopy shows that, within the material, LHC-11 is coupled to PSI for excitation-energy transfer and that this coupling is decreased by the presence of Mg2+, which also decreased PSI electron transport specifically at limiting light intensity. Inclusion of phosphorylated LHC-I1 within the material did not alter its structure, but gave decreased energy transfer to PSI and inhibition of electron transport which was independent of light intensity, implying effects of phosphorylation on both light harvesting and directly on electron transport. Inclusion of Mg2+ within the phosphorylated material gave decreased energy transfer, but slightly increased PSI electron transport. A cation-induced direct promotion of PSI electron transport was also observed in isolated PSI particles. The PSI/LHC-I1 material represents a model system for examining protein interactions during light-state adaptations and the possibility that LHC-I1 can contribute to the antenna of PSI in light state 2 in vivo is discussed.The two types of photosystem operating within the chloroplast thylakoid membrane are connected in series for non-cyclic photosynthetic electron transport and must therefore turn over at equal rates. Photosynthesis will be at its most efficient when the two photosystems receive excitation energy at equal rates. Photosynthetic organisms have evolved an adaptation mechanism, termed state 1 -state 2 transitions, that balances the transfer of excitation energy to the two photosystems, despite variations in light regime. Preferential excitation of photosystem I1 (PSII) gives rise to state 2 and a decrease in energy transfer to PSII relative to photosystem I (PSI). Preferentizl excitation of PSI gives rise to state 1 and an increase in excitation-energy transfer to PSII relative to PSI [l].The transition to state 2 in higher-plant chloroplasts occurs as a result of over reduction of plastoquinone by preferential excitation of PSII. This gives rise to a decrease in the absorption cross-section of PSII, which results in a decrease in the PSII fluorescence yield at room temperature [2--31 and in a decrease in PSII electron transport at limiting light intensity [4]. These effects result from phosphorylation of LHC-I1 by a protein kinase, the activity of which may be coupled to the Changes in cation concentration may also influence excitation-energy distribution [I 8 -201. An earlier mechanistic model for the regulation of excitation-energy distribution involved increased excitation of PSI in state 2. as a result of

show abstract

Section: Resultsmentioning

confidence: 94%

Protein phosphorylation and Mg²⁺influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Harrison

Allen

1992

European Journal of Biochemistry

View full text Add to dashboard Cite

show abstract

“…The midpoint redox potential of HEP II (-375 mV at pH 7) [14] suggests that PS I must be the electron donor. However, while addition of MgCl2 slowed the rate of oxygen uptake with methyl viologen as acceptor (see [21]), it has no effect on the rate with HEP II. The very low concentration of methyl viologen used (1 FM) means that electron transfer to methyl viologen limits the rate of electron transfer, rather than light intensity.…”

Section: Resultsmentioning

confidence: 98%

“…The high lipophilicity and electrical neutrality of HEP II in comparison to methyl viologen, and its ability to interact with PS I, suggest that it will be a very useful 'reduction/oxidation mediator in potentiometric studies on chloroplasts. HEP II will also be useful in studying those effects of Mg2+ on electron transfer through PS I which are thought to be unrelated to interactions with the electron acceptor [21]. Furthermore, HEP II and its analogues appear to have potential applications as electron transfer catalysts in photochemical energy transducers (in preparation).…”

Section: Resultsmentioning

confidence: 99%

Superoxide formation in pea chloroplasts by a dioxathiadiaza‐2,5‐pentalene derivative, a new lipophilic

1984

View full text Add to dashboard Cite

The dioxathiadiaza-2,5-pentalene derivative, HEP II, has herbicidal effects similar to those of methyl viologen. HEP II promotes superoxide formation when added to illuminated pea chloroplasts. Superoxide dismutase, but not catalase, diminished formation of the superoxide whereas cyanide and azide enhanced its formation, presumably by inhibiting the endogenous superoxide dismutase activity. DCMU, which inhibits photosynthetic electron transport, inhibited superoxide formation. Rates of superoxide formation and oxygen uptake were very similar when equal concentrations of methyl viologen or HEP II were added. At subsaturating concentrations of electron acceptor, Mg2+ decreased the rate of oxygen uptake with methyl viologen but not with HEP II, probably reflecting differences in their interactions with the Photosystem I electron donation site. It is likely that HEP II, by analogy with methyl viologen, is reduced by chloroplast Photosystem I and reoxidised by molecular oxygen, generating superoxide. Photosynthesis

show abstract

Differences in Characteristics of Photosystem I and II Complexes from Various Regions of Thylakoid Membranes

Kochubey

Korneev

Shevehenko

1998

Photosynthesis: Mechanisms and Effects

View full text Add to dashboard Cite

Heterogeneity in photosystem I. Evidence from cation-induced decrease in Photosystem I electron transport

Cited by 5 publications

References 15 publications

Protein phosphorylation and Mg²⁺influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Protein phosphorylation and Mg²⁺influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Superoxide formation in pea chloroplasts by a dioxathiadiaza‐2,5‐pentalene derivative, a new lipophilic

Differences in Characteristics of Photosystem I and II Complexes from Various Regions of Thylakoid Membranes

Contact Info

Product

Resources

About

Heterogeneity in photosystem I. Evidence from cation-induced decrease in Photosystem I electron transport

Cited by 5 publications

References 15 publications

Protein phosphorylation and Mg2+influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Protein phosphorylation and Mg2+influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Superoxide formation in pea chloroplasts by a dioxathiadiaza‐2,5‐pentalene derivative, a new lipophilic

Differences in Characteristics of Photosystem I and II Complexes from Various Regions of Thylakoid Membranes

Contact Info

Product

Resources

About

Protein phosphorylation and Mg²⁺influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I

Protein phosphorylation and Mg²⁺influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll‐a/b‐binding light‐harvesting complex of photosystem II and photosystem I