Polypeptide Composition of Photosynthetic Membranes from Chlamydomonas reinhardi and Anabaena variabilis

Euploidy in Ricinus: EUPLOIDY EFFECTS ON PHOTOSYNTHETIC ACTIVITY AND CONTENT OF CHLOROPHYLL-PROTEINS

The effects of nuclear genome duplication on the chlorophyll-protein content and photochemical activity of chloroplasts, and photosynthetic rates in leaf tissue, have been evaluated in haploid, diploid, and tetraploid individuals of the castor bean, Ricinus communis L. Analysis of this euploid series revealed that both photosystem II (2,6-dichlorophenolindophenol reduction) and photosystem I oxygen uptake (N,N,N',N'-tetramethyl-p-phenylenediamine to methyl viologen) decrease in plastids isolated from cells with increasingly larger nuclear complement sizes. Photosynthetic O(2)-evolution and (14)CO(2)-fixation rates in leaf tissue from haploid, diploid, and tetraploid individuals were also found to decrease with the increase in size of the nuclear genome. Six chlorophyll-protein complexes, in addition to a zone of detergent complexed free pigment, were resolved from sodium dodecyl sulfate-solubilized thylakoid membranes from cells of all three ploidy levels. In addition to the P700-chlorophyll a-protein complex and the light-harvesting chlorophyll a/b-protein complex, four minor complexes were revealed, two containing only chlorophyll a and two containing both chlorophyll a and b. The relative distribution of chlorophyll among the resolved chlorophyll-protein complexes and free pigment was found to be similar for all three ploidy levels.

Chlorophyll-Protein Complexes of the Cyanophyte, Nostoc sp

Four chlorophyll-protein complexes have been resolved from the cyanophyte, Nostoc sp., by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis at 4 C. Complexes solubilized by SDS from Spinacia oleracea were run for comparison. As has been well documented, the P700-chlorophyll a-protein complex from the higher plant and blue-green algal samples are similar, and the light-harvesting pigment protein complex is present only in the former. Most noteworthy are two closely migrating chlorophyll proteins in Nostoc sp. which have approximately the same mobility as a single chlorophyll-protein band resolvable from spinach. The absorption maximum of the complex from spinach is at 667 nanometers, and those of the two complexes from Nostoc sp. are at 667 and 669 nanometers; the fluorescence emission maximum at -196 C is at 685 nanometers, and the 735 nanometer fluorescence peak, characteristic of the P700-chlorophyll a-protein complex, is absent. The apoproteins of these new complexes from Nostoc sp. and spinach are in the kilodalton range. It appears that at least one of these two chlorophyll-protein complexes from Nostoc sp. compares with those recently described by others from higher plants and green algae as likely photosystem II complexes, perhaps containing P680, although no photochemical data are yet available.

Electrophoretic and spectrophotometric studies of chlorophyll-protein complexes from tobacco chloroplasts. Isolation of a light harvesting pigment protein complex with a molecular weight of 70,000

Abstract— …After a short‐term solubilization with sodium dodecyl sulphate, chloroplast membranes of tobacco were separated by polyacrylamide gel electrophoresis into three chlorophyll‐protein complexes. In addition to the two major complexes termed I and IIc corresponding respectively to P700 chlorophyll a‐protein and light‐harvesting chlorophyll a/b‐protein described by Thornber (1975), a relatively stable complex termed IIa has been observed. This new complex has an apparent molecular weight of 70,000 daltons and possesses Chl a and b.

Complexes I, IIa and IIC have been isolated and precise spectroscopic analyses have been performed. Fourth derivative analyses of low temperature absorption spectra suggest that complex IIa seems more representative than IIC of chlorophyll a forms present in intact thylakoid membranes.

Moreover, the electrophoretic study reveals that CPI and CPII are composed of only one polypeptidic subunit with respective molecular weights of 68,000 and 24,000 daltons.

Composition of a photosystem I chlorophyll protein complex from Anabaena flos-aquae

The use of Triton X-100 to solubilize membrane fragments from Anabaena flos-aquae in conjunction with DEAE cellulose chromatography allows the separation of three green fractions. Fraction 1 is detergent-solubilized chlorophyll, and Fraction 2 contains one polypeptide in the 15 kdalton area. Fraction 3, which contains most of the chlorophyll and shows P-700 and photosystem I activity, shows by SDS gel electrophoresis varying polypeptide profiles which reflect the presence of four fundamental bands as well as varying amounts of other polypeptides which appear to be aggregates containing the 15 kdalton polypeptide. The four fundamental bands are designated Band I at 120, Band II at 52, Band III at 46, and Band IV at 15 kdaltons. Band I obtained using 0.1% SDS contains chlorophyll and P-700 associated with it. When this band is cut out and rerun, the 120 kdalton band is lost, but significant increases occur in the intensities of Bands II, III, and IV as well as other polypeptides in the 20-30 kdalton range. The use of 1% Triton X-100 coupled with sucrose density gradient centrifugation allows the separation of three green bands at 10, 25 and 40% sucrose. The 10% layer contains a major polypeptide which appears to be Band IV. The 25 and 40% layers show essentially similar polypeptide profiles, resembling Fraction 3 in this regard, except that the 40% layer shows a marked decrease in Band III. Treatment of the material layering at the 40% sucrose level with a higher (4%) concentration of Triton X-100 causes a loss (disaggregation) of the polypeptides occurring in the 60-80 kdalton region and in increase in the lower molecular weight polypeptides. Thus, aggregation of the lower molecular weight polypeptides accounts for the variability seen in the electrophoresis patterns. Possible relations of the principal polypeptides to the known photochemical functions in the original membrane are discussed.

Structure and morphogenesis of photosynthetic membranes. I. Is there a single basic peptide within Zea mays thylakoids?

We have previously given evidence for a physical heterogeneity among proteins from photosynthetic membranes of maize chloroplast [1]. About fifteen components have now been identified, differing in their molecular weights and also in their varying abilities to bind protochlorophyllide and chlorophyll [2]. In this paper, we show that all these proteins have very similar amino acid compositions. A detailed chemical comparison is made between, on one hand the mixture of all proteins and on the other the smallest component of molecular weight 10 000. All the features analysed (percent of non-proteic material, partial peptide maps, N and Cterminal ends and content of linked sugars) are the same in both cases. We conclude from these experiments that it is likely that all components are generated with the same basic peptide unit. This assertion seems to be confirmed by the fact that, after mild alkaline treatment, all the components are converted into the smallest one, as seen by electrophoresis. Thus, within the photosynthesizing membranes, there appears to be a basic structural protein unit, present in a form that is more or less "polymerized". This may account for most of the particular, and sometimes disturbing, properties so far described for this system. It is likely that such a peptide, or a similar one, would provide a framework for all photosynthesizing structures.

The Light-harvesting Chlorophyll a/b-Protein Complex of Chlamydomonas reinhardii

The molecular organization of chlorophyll in Chlamydomonas reinhardii has been shown to be essentially similar to that in higher plants. Some 50% of the chlorophyll in Chlamydomonas reinhardii chloroplast membranes has been shown to be located in a chlorophyll a/b-protein complex. The complex was isolated in a homogeneous form by hydroxylapatite chromatography of sodium dodecyl sulfate extracts of the chloroplast membranes. Its absorption spectrum exhibits two maxima in the red region at 670 and 652 nm due to the presence of equimolar quantities of chlorophylls a and b in the complex. Preparations of the chlorophyll-protein also contain some of each of the carotenoids observed in the intact chloroplast membrane, but not in the same proportions. The native complex (S value = 2.3S) exhibits a molecular weight of 28,000 +/- 2,000 on calibrated sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, on the basis of its amino acid composition and other data a more probable molecular weight of about 35,000 was calculated. Each 35,000 dalton unit contains three chlorophyll a and three chlorophyll b molecules, and on the average one carotenoid molecule conjugated with probably a single polypeptide of 29,000 daltons. Comparison of spectral and biochemical characteristics demonstrates that this algal chlorophyll-protein is homologous to the previously described major light-harvesting chlorophyll a/b-protein of higher plants. It is anticipated that the Chlamydomonas complex functions solely in a light-harvesting capacity in analogy to the function determined for the higher plant component.