Trimeric forms of the photosystem I reaction center complex pre‐exist in the membranes of the cyanobacterium <i>Spirulina platensis</i>

Shubin, Vladimir; Tsuprun, Vladimir; Bezsmertnaya, I. N.; Karapetyan, N. V.

doi:10.1016/0014-5793(93)81685-s

Cited by 80 publications

(48 citation statements)

References 16 publications

(40 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This indicates that around 90% of PS I in intact cells grown at moderate light intensities is present as trimers (Fig. 3B), confirming earlier reports about a (mainly) trimeric in vivo organization of PS I in cyanobacterial cells (5,9). The emission spectrum of cells without dithionite (dashed line) shows that some PS I trimers in dark incubated cells contain P700, which has already been reduced by internal reductants.…”

Section: Isolation and Characterization Of Ps I Trimers And Monomers-supporting

confidence: 75%

“…This Chl gives rise to a 760 nm fluorescence emission peak (F760) at 77 K. Under the same conditions, the monomer of S. platensis, which is similar to all other cyanobaceria, shows only emission peaks at 725-730 nm. Moreover, the intensity of the 760-nm emission band, which is visible only under reducing conditions, reflects directly the redox state of P700 (9,12). The general role of these red Chls in photosynthesis is still completely unknown.…”

Section: Photosystem (Ps)mentioning

confidence: 99%

See 1 more Smart Citation

In Vitro Oligomerization of a Membrane Protein Complex

Kruip

Karapetyan

Терехова

et al. 1999

Journal of Biological Chemistry

View full text Add to dashboard Cite

Many membrane proteins can be isolated in different oligomeric forms. Photosystem I (PSI), for example, exists in cyanobacteria either as a monomeric or as a trimeric complex. Neither the factors responsible for the specific trimerization process nor its biological role are known at present. In the filamentous cyanobacterium Spirulina platensis, trimers in contrast to monomers show chlorophyll fluorescence emission at 760 nm. To investigate the oligomerization process as well as the nature of the long wavelength chlorophylls, we describe here an in vitro reconstitution procedure to assemble trimeric PS I from isolated purified PS I monomers. Monomers (and trimers) were extracted from S. platensis with n-dodecyl ␤-D-maltoside and further purified by perfusion chromatography steps. The isolated complexes had the same polypeptide composition as other cyanobacteria (PsaA-PsaF and PsaI-PsaM), as determined from high resolution gels and immunoblotting. They were incorporated into proteoliposomes, which had been prepared by the detergent absorption method, starting from a phosphatidylcholine:phosphatidic acid mixture solubilized by octylglucoside. After the addition of monomeric PS I (lipid:chlorophyll, 25:1), octylglucoside was gradually removed by the stepwise addition of Biobeads. The 77 K fluorescence emission spectrum of these proteoliposomes displays a long wavelength emission at 760 nm that is characteristic of PS I trimers, which indicates for the first time the successful in vitro reconstitution of PS I trimers. In addition, a high performance liquid chromatography analysis of complexes extracted from these proteoliposomes confirms the formation of structural trimers. We also could show with this system 1) that at least one of the stromal subunits PsaC, -D, and -E is necessary for trimer formation and 2) that the extreme long wavelength emitting chlorophyll is formed as a result of trimer formation.

show abstract

Section: Isolation and Characterization Of Ps I Trimers And Monomers-supporting

confidence: 75%

Section: Photosystem (Ps)mentioning

confidence: 99%

In Vitro Oligomerization of a Membrane Protein Complex

Kruip

Karapetyan

Терехова

et al. 1999

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…In contrast to higher plants, in which only the monomer form of PSI RC is present (Golbeck, 1992;Chitnis, 1996), in cyanobacteria both monomeric and trimeric forms of PSI RCs exist (Rö gner et al, 1990a;Shubin et al, 1993;Boekema et al, 1994). On the other hand, dimerization of PSI could not be observed.…”

mentioning

confidence: 70%

Phosphatidylglycerol Is Essential for Oligomerization of Photosystem I Reaction Center

et al. 2004

View full text Add to dashboard Cite

Our earlier studies with the pgsA mutant of Synechocystis PCC6803 demonstrated the important role of phosphatidylglycerol (PG) in PSII dimer formation and in electron transport between the primary and secondary electron-accepting plastoquinones of PSII. Using a long-term depletion of PG from pgsA mutant cells, we could induce a decrease not only in PSII but also in PSI activity. Simultaneously with the decrease in PSI activity, dramatic structural changes of the PSI complex were detected. A 21-d PG depletion resulted in the degradation of PSI trimers and concomitant accumulation of monomer PSI. The analyses of PSI particles isolated by MonoQ chromatography showed that, following the 21-d depletion, PSI trimers were no longer detectable in the thylakoid membranes. Immunoblot analyses revealed that the PSI monomers accumulating in the PG-depleted mutant cells do not contain PsaL, the protein subunit thought to be responsible for the trimer formation. Nevertheless, the trimeric structure of PSI reaction center could be restored by readdition of PG, even in the presence of the protein synthesis inhibitor lincomycin, indicating that free PsaL was present in thylakoid membranes following the 21-d PG depletion. Our data suggest an indispensable role for PG in the PsaL-mediated assembly of the PSI reaction center.Phosphatidylglycerol (PG) is an integral component of photosynthetic membranes. PG molecules are important for both the formation and functioning of photosynthetic apparatus. In cyanobacterial cells, PG is the only representative of the phospholipid family (Wada and Murata, 1998), and the majority of PG molecules are localized in the thylakoid membranes that are the site of oxygenic electron transport. Photosynthesis is the basic energy source of cyanobacteria and generally for photosynthetic organisms. The availability of the complete genomic sequence of Synechocystis PCC6803 (Kaneko et al., 1996) opened the way for studying the structural and functional roles of PG via molecular genetic approaches. The pgsA gene encoding PG phosphate synthase was inactivated in Synechocystis PCC6803 cells by inserting a kanamycin resistance gene cassette (Hagio et al., 2000). Maintenance of the recently generated pgsA mutant strain requires exogenously supplied PG. A 40% decrease in photosynthetic oxygen-evolving activity could be detected following a 3-d depletion of PG, which resulted in an approximately 50% decrease in the amount of PG molecules in the cellular membranes. The photosynthetic processes, as measured by fluorescence induction in the PG-depleted cells, slowed down, and a perturbation of the surroundings of the secondary quinone acceptor (Q B ) was observed (Gombos et al., 2002). This perturbation was similar to the effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), which can block electron transport between primary quinone acceptor (Q A ) and Q B . Additionally, Fragata et al. (1991) demonstrated that in isolated barley (Hordeum vulgare) PSII particles, oxygen-evolving activity strongly depends on the pr...

show abstract

“…System I1 indicates a dimeric structure which represents two PS I1 units [85]. Possibly the trimer of PS I and the dimer of PS I1 are the active form in vivo [86]. …”

Section: Structural Organization Of the Photosynthetic Systemsmentioning

confidence: 99%

Primary reactions of oxygenic photosynthesis

Witt

1996

Ber Bunsenges Phys Chem

View full text Add to dashboard Cite

Trimeric forms of the photosystem I reaction center complex pre‐exist in the membranes of the cyanobacterium Spirulina platensis

Cited by 80 publications

References 16 publications

In Vitro Oligomerization of a Membrane Protein Complex

In Vitro Oligomerization of a Membrane Protein Complex

Phosphatidylglycerol Is Essential for Oligomerization of Photosystem I Reaction Center

Primary reactions of oxygenic photosynthesis

Contact Info

Product

Resources

About