Presence of Polypeptides of Cytoplasmic and Chloroplastic Origin in Isolated Photoactive Preparations of Photosystems I and II in <i>Chlamydomonas reinhardi</i> y-1

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Photosystem II activity, development, and organization were studied in membranes from dark-adapted Euglens gracilis Klebs var. Z Pringsheim cells during a modulated greening process of light-dark-light cycles. The results obtained from measurements of overlapping partial photosystem II (PSII) reactions (fluorescence induction parameters, quantum yield, flash yield, and maximal rate of H20 -. 2,6-dichlorophenolindophenol IDCIPI and 1,5-diphenylcarbazide IDPCI -* DCIP reactions) during these cycles indicate the formation of active PSII units in the dark. The necessity for proteins from the chloroplast translational machinery for this formation is evidenced by the inhibition of synthesis of the PSII units in chloramphenicol-treated cells. The effect of this drug, both during the dark and second light periods, can be summarized as follows: (a) disruption of the electron transfer connection to the plastoquinone pool, or decrease in the pool size; (b) loss of excitation energy transfer efficiency in the second light period; (c) impairment of the 02 evolution apparatus, as shown by comparison of the efficiency of DCP and H20 as electron donors.These conclusions are based on the use of a previously developed method of measurement and analysis of data (Cahen et al. 1976 Plant Physiol 58: 257-267).

Section: Resultssupporting

confidence: 69%

Development and Repair of Photosystem II Activity in Normal and Chloramphenicol-treated Euglena gracilis Cells

Malkin¹,

Gurevitz²,

Ohad³

1978

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“…However, the formation of CPII (LHC) and the presumed 708 nm complex required only cytoplasmic polypeptides. (5,16), are heavily labeled in the control in presence of CAP, as reported previously (4). In addition, several minor polypeptides were also significantly labeled and were identified from their electrophoretic mobility as polypeptides 9, probably 14, 15, and 21 (16).…”

Section: Chl-protein Complexes Of Chlamydomonassupporting

confidence: 56%

“…Several labeled bands appeared in all conditions in which photosynthetic electron flow was reestablished. These include polypeptides 2, 4.1, 4.2, 5, 6, and possibly 12, and DI (4,18 (4,19). Indeed, C. reinhardi mutants lacking polypeptide 2 which has the kD value of -66, were shown to have a very low PSI activity (19).…”

Section: Chl-protein Complexes Of Chlamydomonasmentioning

confidence: 99%

Functional Organization of the Chlorophyll-Containing Complexes of Chlamydomonas reinhardi

Gershoni

Shochat²,

Malkin³

et al. 1982

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The stepwise synthesis and assembly of photosynthetic membrane components in the y-l mutant of Chiamydomonas reinhardi have been previously demonstrated (Ohad 1975 In Membrane Biogenesis, Mitochondria, Chlo-roplasts and Bacteria, Plenum, pp . This experimental system was used here in order to investigate the process of formation and interconnection of the energy collecting chlorophylls with the reaction centers of both photosystems I and II. The following measurements were carried out: photosynthetic electron flow at various light intensities, including parts or the entire electron transfer chain; analysis of the kinetics of fluorescence emission at room temperature and fluorescence emission spectra at 77 K, and electrophoretic separation of membrane polypeptides and chlorophyll protein complexes. Based on the data obtained it is concluded that: (a) each photosystem (PSI and PSII) contains, in addition to the reaction center, an interconnecting antenna and a main or Ught harvesting antenna complex; (b) the formation of the light harvesting complex, interconnecting antenna, and reaction centers for each photosystem can occur independently. (c) the interconnecting antennae lnk the light harvesting complexes with the respective reaction centers. In their absence, energy transfer between the light harvesting chlorophylis and the reaction centers is inefficient. The formation of the interconnecting antennae and efficient assembly of photosystem components occur simultaneously with the de novo synthesis of chlorophyll and at least three polypeptides, one translated in the cytoplasm and two translated in the chloroplast. The synthesis of these polypeptides was found to be light dependent.The greening process of the y-l mutant of Chlamydomonas reinhardi as well as, e.g., of Euglena (21, 22, 25), Scendesmus (9, 11), and higher plants (3), forms a valuable tool for the study of the connection and interrelation of the various parts of the photosynthetic apparatus, notably the antennae pigments, reaction centers, and electron transfer components (5,15,30).Dark-grown Chlamydomonas y-l cells contain only small amounts of Chl and photosynthetic membrane remnants (30

“…Mutants lacking LHCP have been most useful in establishing the light-harvesting function of this complex since such plants continue photosynthesis at high rates even in the complete absence of the complex (35). Although most reported mutations eliminating P700-CP are extranuclear (presumably in the plastid DNA) and most mutations affecting LHCP are nuclear, occasional observations of the reverse situation indicate a role for both the nuclear and the plastid DNAs in the synthesis and assembly of both complexes into the membrane as previously suggested (4).…”

mentioning

confidence: 80%

Effect of Nuclear Mutation in Maize on Photosynthetic Activity and Content of Chlorophyll-Protein Complexes

Miles¹,

Markwell²,

Thornber³

1979

A number of new nuclear mutants have been isolated from maize by selection for high chlorophyll (Chl) fluorescence. These mutants show reduced rates of photosynthesis and/or are deficient in Chli. Electrophoretic examination of wild type thylakoid membranes revealed five Chi-protein complexes, two containing only Chi a and three containing Chli a and Chi b. A class of nonviable, photosystem I-deficient mutants was found to be lacking one (A-1) of the two Chl a-protein complexes. A second class of nonviable, photosystem I-lacking mutants was found to be missing not only this A-1 complex but also one or more of the three Chi a and b-containing, light-harvesting Chl-protein complexes. Viable mutants were obtained which appeared to have lost just one of the Chi b-containing complexes, whereas a second class of viable mutants was missing all three of the Chi b-complexes. The results confirm that the A-1 band is associated with the P700-Chl a-protein complex characterized previously. The data also indicate the existence of structurally different forms of the light-harvesting Chi a-and b-containing complexes. The results also show a lower molecular weight band (A-2) containing primarily Chi a and which appears to be required for viability.