Comparative study of the circular dichroism spectra of reaction centers from several photosynthetic bacteria

Philipson, Kenneth D.; Sauer, Kenneth

doi:10.1021/bi00727a028

Cited by 68 publications

(30 citation statements)

References 22 publications

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“…This observation agrees with the interpretation that the absorption at 850 nm represents the second dlmer band of the special parr [1,9,10]. CD investigations [11], studies of oriented cells [12], and our measurements on crystals with polarized light (see below) lead to the same conclusions The small absorption band at 680 nm is an oxidation product of BChl b [2]. Special care m avoiding oxygen during the preparation reduces this minor absorption band.…”

supporting

confidence: 89%

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Zinth¹,

Kaiser²,

Michel

1983

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Crystallized reaction centers from Rhodopseudomonas viridis (i) are photochemicaily active with electron transfer from the special pair to the quinones, (ii) show dichroism giving valuable.information on the orientation of the different chromophores and (iii) allow chemical treatment in the crystalline phase.In the past, reaction centers from photosynthetic bacterm have been investigated m intact cells, in photosynthetic membranes or isolated m detergent solutions. Comparison of the optical spectra of intact cells with those of isolated reaction centers suggested that careful ~solatlon does not seriously affect the properties of the reaction centers [1][2][3][4][5][6]. The spectral properues and the pigment composmon of isolated reaction centers from Rhodopseudomonas vtrtdts have been studied extenswely [1-6] Recently, the photosynthetic reaction centers from thas photosynthetic bacterium were crystallized [7]. In this paper we report on the properties of these crystals Reaction centers isolated w~th the detergent N,N-dlmethyldodecylarmne N-oxide contain four BChl b and two BPh b molecules [1] The primary electron donor, called P-960 due to its maxamum of absorbance, is made up of two of the four BChl b molecules, whale the 'primary' electron acceptor is a qulnone-lron complex [1]. There are one menaqumone and one to two ub~qumones per P-960 [8]. Isolated reacUon centers from Rps vtrt-A bbrevlatlons BChl, bactenochlorophyll, BPh, bactenopheophytm dts also contain four heme groups (two 'cytochrome c-558' and two 'cytochrome c-553'), wluch are probably bound to the same protein subumt [6], They feed electrons to P-960 +.The reaction centers were ~solated as described recently with the following modification [7]. For the molecular sieve chromatography step we used as column material Fractogel TSK HW 55 S (Merck, Darmstadt), thus step was repeated. In contrast to earher preparations [7] using different column material, we now observe bleaching of P-960 upon lllumanatlon Thus finding indicates that the qumones are still present in the new preparations. The crystals were grown as described previously [7]. The space group of these crystals IS P4~(3)2~2 with a tetragonal unit cell dlmens~on of 223 × 223 x 114 ,~ containing eight asymmetric umts per crystallographac umt cell. The volume of the asymmetric umt and the molecular wetght of the reactton centers make it more hkely that each asymmetric umt ~s occupied by two reaction center molecules than by one or three With these figures were calculate 2.8-l0 )8 reaction center molecules per cm 3, corresponding to 4.7-l0 -3 mol/1. In space group P41(3)212, a 4-fold screw axas is parallel to the z-direction whereas nomntersectlng 2-fold screw axes (perpen&cular to the 4-fold axis) are 0005-2728/83/0000-0000/$03 00

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supporting

confidence: 89%

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Zinth¹,

Kaiser²,

Michel

1983

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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“…3 (23). Circular dichroism (8)(9)(10)(11), and electron paramagnetic resonance measurements (12,13) indicate the presence of at least two strongly coupled bacteriochlorophyll molecules in reaction centers isolated from purple bacteria. Circular dichroism difference spectra (11) …”

Section: Methodsmentioning

confidence: 99%

The Crystal and Molecular Structure of Ethyl Chlorophyllide a ·2H ₂ O and Its Relationship to the Structure and Aggregation of Chlorophyll a

Strouse

1974

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

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Determination of the crystal structure of ethyl chlorophyllide a-2H20 by single crystal x-ray diffraction techniques has provided the first detailed molecular structural data available for a magnesium-containing derivative of chlorophyll. At the same time the aggregation observed in this structure serves as the basis for a model of chlorophyll aggregation in vitro and in vivo. The magnesium atom in ethyl chlorophyllide is displaced 0.4 A from the plane of the chlorin ring in the same direction as the methyl ester substituent. A water molecule occupies the fifth coordination site. A second water molecule is hydrogen bonded to the coordinated water molecule and also to the carbonyl oxygen atom of the methyl ester. Hydrogen bonds between the water molecules and carbonyl oxygen atoms link the chlorophyllide molecules into a two-dimensional aggregate of crosslinked one-dimensional polymers. The relationship of this aggregate to aggregates of chlorophyll both in vitro and in vivo is discussed, as is the efficiency of exciton transport within the polymer.Prompted by the key role of chlorophylls in photosynthetic processes, numerous investigators have studied the structure and function of these pigments both in vivo and in vitro. The complete synthesis of chlorophyll a by Woodward (1) crowned an early sequence of structural studies. A vast amount of information has been provided by the application of modern physical techniques. Infrared and magnetic resonance measurements (2, 3) have been used to great advantage and x-ray structural investigations (4, 5) have been carried out on several degradation products. These studies have not, however, provided an unambiguous model for the detailed molecular structure of chlorophyll or any magnesium-containing derivative.As a result of various studies designed to determine the nature and environment of chlorophyll in photosynthetic systems, it is now widely accepted (6-11) that chlorophyll aggregates play important roles in photosynthesis. An early model of the chloroplast lamellae (7) envisioned a two-dimensional aggregate of chlorophyll molecules at the interface between protein and lipid layers. This model was based primarily on the similarity of the position of the red absorption maximum in the visible spectrum of chlorophyll in vivo to that observed for chlorophyll aggregates in vitro. While chlorophyll in vivo may occur in a variety of environments and the shifts of the red absorption band may arise from combinations of chlorophyll-protein and chlorophyll-chlorophyll interactions, recent investigations (8-13) have provided convincing evidence for the existence of chlorophyll aggregates in several types of photosynthetic material. It is clear that an understanding of the nature of chlorophyll aggregation is of prime importance in an understanding of the molecular processes involved in the initial stages of photosynthesis.In most respects the alkyl chlorophyllidest serve as excellent models of chlorophyll. Visible absorption spectra, nuclear magnetic resonance spectra a...

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“…The microscopic integrity of LH1 and associated pigments was analyzed by near-IR CD, which has previously been shown to be a fingerprint for pigment-pigment interactions in the Q y region (10,24,26,47,54). The near-IR CD spectra of isolated chromatophores from S1 grown anaerobically and semiaerobically (Fig.…”

Section: Gene Deletion and Southern Hybridization Analysismentioning

confidence: 99%

The Reaction Center H Subunit Is Not Required for High Levels of Light-Harvesting Complex 1 in Rhodospirillum rubrum Mutants

Lupo

Ghosh

2004

J Bacteriol

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The gene (puhA) encoding the H subunit of the reaction center (RC) was deleted by site-directed interposon mutagenesis by using a kanamycin resistance cassette lacking transcriptional terminators to eliminate polar effects in both the wild-type strain Rhodospirillum rubrum S1 and the carotenoid-less strain R. rubrum G9. The puhA interposon mutants were incapable of photoheterotrophic growth but grew normally under aerobic chemoheterotrophic conditions. Absorption spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the RCs were absent. In minimal medium and also in modified medium containing succinate and fructose, the light-harvesting 1 complex (LH1) levels of the S1-derived mutants were about 70 to 100% of the wild-type levels in the same media. The correct assembly of LH1 in the membrane and the pigment-pigment interaction were confirmed by near-infrared circular dichroism spectroscopy. LH1 formation was almost absent when the carotenoid-less G9-derived puhA mutants were grown in standard minimal medium, suggesting that carotenoids may stabilize LH1. In the fructose-containing medium, however, the LH1 levels of the G9 mutants were 70 to 100% of the parental strain levels. Electron micrographs of thin sections of R. rubrum revealed photosynthetic membranes in all mutants grown in succinate-fructose medium. These studies indicate that the H subunit of the RC is necessary neither for maximal formation of LH1 nor for photosynthetic membrane formation but is essential for functional RC assembly.It is well established that in phototrophic purple bacteria the photosynthetic unit is expressed in a specialized intracytoplasmic membrane (ICM) (16,18) and is composed of a reaction center (RC) surrounded by a light-harvesting complex (1,17,44). Although most phototrophic bacteria contain two kinds of light-harvesting complexes, light-harvesting complex 1 (LH1) and light-harvesting complex 2 (LH2), only one of these, LH1, is in intimate contact with the RC. Recent structural studies (6,20,22,25,31,36,37,43,(59)(60)(61) have indicated that the component ␣␤ dimers of LH1, each of which binds two bacteriochlorophyll (BChl) molecules and at least one molecule of carotenoid, form a ring around the RC. For Rhodospirillum rubrum (33,37,59,61) and Blastochloris viridis (previously called Rhodopseudomonas viridis) (60), both of which contain only a single light-harvesting complex, LH1 appears to completely surround the RC. In Rhodobacter sphaeroides, however, recent electron micrographic evidence (36) has suggested that the LH1 in this organism may not be completely closed, although the low resolution of the data in this study may not have been sufficient to allow a definite conclusion to be drawn. In all cases, however, it appears that the assembly of RCs and LH1 in vivo is always perfectly coordinated, and neither biochemical nor spectroscopic evidence has indicated the presence of empty LH1 rings or incorrectly assembled RCs. A continuing puzzle, therefore, concerns the mechanism of assembly of...

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Comparative study of the circular dichroism spectra of reaction centers from several photosynthetic bacteria

Cited by 68 publications

References 22 publications

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

The Crystal and Molecular Structure of Ethyl Chlorophyllide a ·2H ₂ O and Its Relationship to the Structure and Aggregation of Chlorophyll a

The Reaction Center H Subunit Is Not Required for High Levels of Light-Harvesting Complex 1 in Rhodospirillum rubrum Mutants

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Comparative study of the circular dichroism spectra of reaction centers from several photosynthetic bacteria

Cited by 68 publications

References 22 publications

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

The Crystal and Molecular Structure of Ethyl Chlorophyllide a ·2H 2 O and Its Relationship to the Structure and Aggregation of Chlorophyll a

The Reaction Center H Subunit Is Not Required for High Levels of Light-Harvesting Complex 1 in Rhodospirillum rubrum Mutants

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The Crystal and Molecular Structure of Ethyl Chlorophyllide a ·2H ₂ O and Its Relationship to the Structure and Aggregation of Chlorophyll a