Synthesis of photosynthetic membrane proteins directed by RNA from rough thylakoids of <i>Chlamydomonas reinhardtii</i>

Margulies, Maurice M.

doi:10.1111/j.1432-1033.1983.tb07821.x

Cited by 22 publications

(5 citation statements)

References 43 publications

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“…This model is supported by two lines of evidence. First, chloroplast polysomes synthesizing subunits of PSII and other thylakoid membrane proteins cofractionated with thylakoid membranes on sucrose density gradients (Chua et al, 1973(Chua et al, , 1976Margulies andMichaels, 1974, 1975;Margulies et al, , 1987Yamamoto et al, 1981;Margulies, 1983;Herrin and Michaels, 1985;Breidenbach et al, 1988;Klein et al, 1988;Zhang et al, 1999). These membranes were proposed to be stroma thylakoids based on results of thylakoid fractionation experiments (Yamamoto et al, 1981;Leto et al, 1985;Mattoo and Edelman, 1987;Adir et al, 1990;van Wijk et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Photosystem II Assembly and Repair Are Differentially Localized inChlamydomonas

Uniacke

Zerges

2007

The Plant Cell

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Many proteins of the photosynthesis complexes are encoded by the genome of the chloroplast and synthesized by bacteriumlike ribosomes within this organelle. To determine where proteins are synthesized for the de novo assembly and repair of photosystem II (PSII) in the chloroplast of Chlamydomonas reinhardtii, we used fluorescence in situ hybridization, immunofluorescence staining, and confocal microscopy. These locations were defined as having colocalized chloroplast mRNAs encoding PSII subunits and proteins of the chloroplast translation machinery specifically under conditions of PSII subunit synthesis. The results revealed that the synthesis of the D1 subunit for the repair of photodamaged PSII complexes occurs in regions of the chloroplast with thylakoids, consistent with the current model. However, for de novo PSII assembly, PSII subunit synthesis was detected in discrete regions near the pyrenoid, termed T zones (for translation zones). In two PSII assembly mutants, unassembled D1 subunits and incompletely assembled PSII complexes localized around the pyrenoid, where we propose that they mark an intermediate compartment of PSII assembly. These results reveal a novel chloroplast compartment that houses de novo PSII biogenesis and the regulated transport of newly assembled PSII complexes to thylakoid membranes throughout the chloroplast.

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Section: Introductionmentioning

confidence: 99%

Photosystem II Assembly and Repair Are Differentially Localized inChlamydomonas

Uniacke

Zerges

2007

The Plant Cell

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“…In algae, the rubisco large subunit (LSU) is targeted to the pyrenoid, a spherical chloroplast compartment specializing in CO 2 fixation (11); however, little is known about the targeting mechanisms involved. We do know that thylakoid membrane proteins are synthesized by membrane-bound chloroplast polysomes (12,13). A chloroplast homolog of the SRP subunit that binds the signal sequence, cpSRP54, has been shown to bind the nascent chain of the D1 subunit of photosystem II (PSII) in a reconstituted chloroplast translation system and to be required for thylakoid membrane biogenesis (14)(15)(16)(17).…”

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confidence: 99%

Chloroplast protein targeting involves localized translation in Chlamydomonas

Uniacke

Zerges²

2009

Proc. Natl. Acad. Sci. U.S.A.

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The compartmentalization of eukaryotic cells requires that newly synthesized proteins be targeted to the compartments in which they function. In chloroplasts, a few thousand proteins function in photosynthesis, expression of the chloroplast genome, and other processes. Most chloroplast proteins are synthesized in the cytoplasm, imported, and then targeted to a specific chloroplast compartment. The remainder are encoded by the chloroplast genome, synthesized within the organelle, and targeted by mechanisms that are only beginning to be elucidated. We used fluorescence confocal microscopy to explore the targeting mechanisms used by several chloroplast proteins in the green alga Chlamydomonas. These include the small subunit of ribulose bisphosphate carboxylase (rubisco) and the light-harvesting complex II (LHCII) subunits, which are imported from the cytoplasm, and 2 proteins synthesized in the chloroplast: the D1 subunit of photosystem II and the rubisco large subunit. We determined whether the targeting of each protein involves localized translation of the mRNA that encodes it. When this was the case, we explored whether the targeting sequence was in the nascent polypeptide or in the mRNA, based on whether the localization was translation-dependent or -independent, respectively. The results reveal 2 novel examples of targeting by localized translation, in LHCII subunit import and the targeting of the rubisco large subunit to the pyrenoid. They also demonstrate examples of each of the three known mechanismsposttranslational, cotranslational (signal recognition particle-mediated), and mRNA-based-in the targeting of specific chloroplast proteins. Our findings can help guide the exploration of these pathways at the biochemical level.chloroplast ͉ FISH ͉ organelle ͉ protein targeting ͉ translation

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“…These leader sequences are clipped either concomitantly with transport into the organelle, or, after transport, perhaps concomitantly with the assembly of the polypeptide into the thylakoid membrane [33 ]. Chloroplast-encloded thylakoid membrane polypeptides may be synthesized on thylakoid bound ribosomes and inserted co-translationally into the membrane [60,94].…”

Section: Synthesis Of Cf1mentioning

confidence: 99%

Photosynthetic ATPases: purification, properties, subunit isolation and function

Merchant

Selman

1985

Photosynth Res

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Photosynthetic coupling factor ATPases (F1-ATPases) generally censist of five subunits named α, β, γ, δ and ε in order of decreasing apparent molecular weight. The isolated enzyme has a molecular weight of between 390,000 to 400,000, with the five subunits probably occurring in a 3:3:1:1:1 ratio. Some photosynthetic F1 ATPases are inactive as isolated and require treatment with protease, heat or detergent in order to elicit ATPase activity. This activity is sensitive to inhibition by free divalent cations and appears to be more specific for Ca(2+) vs. Mg(2+) as the metal ion substrate chelate. This preference for Ca(2+) can be explained by the higher inhibition constant for inhibition of ATPase activity by free Ca(2+). Methods for the assay of a Mg-dependent ATPase activity have recently been described. These depend on the presence of organic solvents or detergents in the reaction mixture for assay. The molecular mechanism behind the expression of either the Ca- or Mg-ATPase activities is unknown. F1-ATPases function to couple proton efflux from thylakoid membranes or chromatophores to ATP synthesis. The isolated enzyme may thus also be assayed for the reconstitution of 'coupling activity' to membranes depleted of coupling factor 1.The functions of the five subunits in the complex have been deduced from the results of chemical modification and reconstitution studies. The δ subunit is required for the functional binding of the F1 to the F0. The active site is probably contained in the β (and α) subunit(s). The proposed functions for the γ and ε subunits are, however, still matters of controversy. Coupling factors from a wide variety of species including bacteria, algae, C3 and C4 plants, appear to be immunologically related. The β subunits are the most strongly related, although the α and γ subunits also show significant immunological cross-reactivity. DNA sequence analyses of the genes for the β subunit of CF1 have indicated that the primary sequence of this polypeptide is highly conserved. The genes for the polypeptides of CF1 appear to be located in two cellular compartments. The α, β and ε subunits are coded for on chloroplast DNA, whereas the γ and δ subunits are probably nuclear encoded. Experiments involving protein synthesis by isolated chloroplasts or protein synthesis in the presence of inhibitors specific for one or the other set of ribosomes in the cell suggest the existence of pools of unassembled CF1 subunits. These pools, if they do exist in vivo, probably make up no greater than 1% of the total CF1 content of the cell.

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Synthesis of photosynthetic membrane proteins directed by RNA from rough thylakoids of Chlamydomonas reinhardtii

Cited by 22 publications

References 43 publications

Photosystem II Assembly and Repair Are Differentially Localized inChlamydomonas

Photosystem II Assembly and Repair Are Differentially Localized inChlamydomonas

Chloroplast protein targeting involves localized translation in Chlamydomonas

Photosynthetic ATPases: purification, properties, subunit isolation and function

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