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Polypeptide and pigment composition

The functional test for PSI-RC can be either the photobleaching of P-700, monitoring the photooxidation of the primary donot Dj j and the transfer of the electron to a stable acceptor or the photoreduction of NADP in the overall activity of PSI. For this latter activity soluble components of the electron transfer chain must be added, such as plastocyanin (plus ascorbate) for electron donation to the RC, and ferredoxin and NADP -ferredoxin oxidoreductase as terminal electron acceptors. This activity was fully present in the PSI-RC preparation of Bengis and Nelson [42], [Pg.105]

The digitonin preparation of PSI-RC has also been demonstrated to be able to catalyze a light-induced proton uptake when incorporated in phospholipid liposomes and illuminated in the presence of ascorbate and phenazine methosulphate [47] incorporation of chloroplast ATPase in the same system yielded the reconstitution of photophosphorylation in a model system. The PSI-RC preparation therefore seems to possess all the functional features of PSI for the vectorial transmembrane electron transfer [48] (see Fig. 4.7). [Pg.106]

The bleaching of P-700 upon illumination corresponds to the production of an oxidized species that has been proposed to be a chlorophyll a dimer. The same bleaching can be obtained by chemical oxidation and titrates with a midpoint potential of about 0.45 V [49,50). The total differential spectrum of P-700 photooxidation presents, in addition to a major band at about 700 nm, a minor band at 685 nm and another in the Soret region at 435 nm. This spectrum has been attributed to chlorophyll a [51], although the presence of a new chlorophyll species in P-700-enriched preparations has been claimed [52]. [Pg.106]

The basis of the concept of a dimer of chlorophyll a in P-700 rests on evidence obtained with optical or ESR spectroscopy. In the P-700 redox difference spectrum, although very similar to that obtainable upon chemical oxidation of chlorophyll a, there are significant differences in the red region, which presents a splitting of the peak (at 685 and 700 nm) which is absent in chlorophyll a [53]. Moreover, the ESR and ENDOR spectra also present characteristics that have been interpreted as due to a dimeric arrangement [16]. Alternative interpretations have been offered suggesting that the spectral distortions are caused by a modification of the chemical environment of chlorophyll a in the RC complex. Definitively not in line with the dimer hypothesis is the spectrum of the light-induced triplet state of P-700, that can be observed when the intermediate acceptor is prereduced chemically in this spectrum the zero field parameters are the same as those of chlorophyll a monomers [54]. It is not clear, however, whether the triplet state resides on P-700 or on other chlorophylls of the RC complex. [Pg.106]

Under the same conditions in which bacteriopheophytin was identified in bacterial RC as the intermediate A, i.e., under reducing conditions in which all other acceptors were prereduced ( — 0.75 V), an absorbance change could be detected in PSI-RC preparations [55]. This change decayed in 1 ms at 5°C, and could be observed also in RC preparations treated with SDS, that had therefore lost all the Fe-S center proteins [56]. The redox potential of this intermediate has been not determined so far. [Pg.107]


In this study we report the influence of severe Cu deficiency in pea plants on PSII and PSI electron transport, polypeptide and pigment composition of thylakoid membranes. In addition, we analyzed the presence of Cu in PSII and LHCII. [Pg.303]

Although major progresses have been recently made, still some basic features of the structural and molecular organization of chi a/b binding proteins such as polypeptide and pigment composition are not well defined. In this study we describe the use of improved analytical methods for the isolation and characterization of chlorophyll-proteins. Their use offers new possibilities to investigate the organization of the PSII antenna system. [Pg.1167]

The polypeptide and pigment protein complexes composition of control and Cu-depleted PSII particles and thylakoids was analysed by gel electrophoresis. For pigment-proteins we obtained the percentage distribution of Chi among the different types of complexes( LHCP, CPI and CPa) and free Chi. Cu deficiency decreases the proportion of Chi in the PSII antenna complex (LHCII or LHCP) from 62 a 47% in thylakoids and from 74 to 62% in PSII particles, and there is a increase in free chlorophyll Fig. 1 shows polypeptide composition of thylakoids, PSII particles and LHCII purified by the method of Burke (11). Special staining for Cu-containing proteins (12), identify only three polypeptides in every preparation. These polypeptides have a apparent molecular (MG) of 32, 30 y 29 kD, and they were associated with the PSII antenna complex. We have not found differences in polypeptides between control and Cu-deficient thylakoids, but in PSII particles isolated from Cu-depleted pea plants... [Pg.305]

In the present study we have used the chi b-less mutant of Chlamydomonas reinhardtii strain cbnl-48 to clarify the role of chi b and carotenoids in the assembly of LHC II. The thylakoids of the chi b-less mutant present a distinct pigment composition and a specific LHC II polypeptide pattern. LHC II from thylakoid membranes of the mutant could not be resolved by mildly dissociating SDS-PAGE. However we reconstituted the LHC II from delipidated chi b-less mutant thylakoids with the pigment extract derived from wildtype thylakoids. Similar to the native LHC II this reconstituted LHC II bind chi b and transfer light energy from chi b to chi a. [Pg.1809]

A coherent interpretation for many experimental results was provided by the concept of a PS I reaction centre. This centre has now been isolated, albeit perhaps not in a definitely pure state. It is made up of a few hydrophobic polypeptides, the primary donor (P-700), several electron acceptors (Fig. 2), and about 50 molecules of pigment (chlorophyll a and /3-carotene). This composition is analogous to that of other types of reaction centres. [Pg.65]

Knoetzel J and Reusing L (1990) Characterisation of the photo synthetic apparatus from the marine dinoflageUate Gonyaulaxpolyedra I. Pigment and polypeptide composition ofthe pigment-protein complexes. J Plant Physiol 136 271-279... [Pg.97]

CP24 resolved from NaSCN treated PSII membranes by mild electrophoresis, was found to consist of only one polypeptide with the apparent molecular weight of 20 kDa (Fig. 1, lane D). When CP24 was isolated from untreated PSII membranes, it showed a multipolypeptide composition and thus the identity of the pigment binding polypeptide(s) could not be firmly established. This problem was overcome by the NaSCN treatment which removes several extrinsic polypeptides contaminating the CP24. [Pg.1212]

Table 1. Summary of the pigment and polypeptide composition and aggregation behaviour of the outer and Inner LHC II pool collected after non-denturing Isoelectric focusing of Isolated bulk LHC II. Table 1. Summary of the pigment and polypeptide composition and aggregation behaviour of the outer and Inner LHC II pool collected after non-denturing Isoelectric focusing of Isolated bulk LHC II.
Tlie polypeptide compositions of the PS I and CCI pi ent-protein bands is similar to those obtained previously for other organisms (1,3,7,13) Note, however, that PS I does not contain any LHC Ilb subunits, a frequent contaminant of PS I preparations, wfrich we ascribe to our not using Triton-XlOO for the purification of PS I. The polypeptide composition of the LHC I pigmented band represents those PS I protein subunits that are not contained in CC I. This then indicates that the LHC I pigment-protein complex indeed contains components of the PS I antenna. The 21kD polypeptide, the LHC Ib apoprotein, is often seen as a doublet. [Pg.1245]

Fig. 1 A) Separation of chlorophyll-p rotein complexes, CPl, LHCPl (Ll), LHCPx (Lx), CPa, LHCP3 (L3) and free pigments (FP). B) 2D-gel showing the polypeptidic composition of the different chlorophyll-protein complexes after coomassie blue staining. C) Schematic map of the 2D-separation. Fig. 1 A) Separation of chlorophyll-p rotein complexes, CPl, LHCPl (Ll), LHCPx (Lx), CPa, LHCP3 (L3) and free pigments (FP). B) 2D-gel showing the polypeptidic composition of the different chlorophyll-protein complexes after coomassie blue staining. C) Schematic map of the 2D-separation.
Plcorel R, Belanger G and Gingras G (1983) Antenna holochrome B880 of Rhodosplrillum rubrum SI. Pigment, phospholipid, and polypeptide composition, Biochemistry 22, 2491-2497. [Pg.196]

Polypeptide Composition of Wild-type Cells and Mutants. The PBS of A. nidulans were analyzed on SDS-PAGE (Fig. 2). Phycobilisomes of WT, in addition to the pigmented bands of PC and APC, had uncolored polypeptides of 80, (70-50), 40, 36 and 31 kD. The polypeptides 80 kD (probable anchor with the thylakold) and 31 kD were present in all PBS. In the PBS of 85Y and 19Y the polypeptides of 36 and 40 kD were absent. These were the mutants with the lowest PC content. In 59G only polypeptide 36 kD was greatly reduced. The nature and function of the polypeptides at 70-50 kD (prevelant in the mutants) is not known. [Pg.696]


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