Mutant carotenoidless

Illumination of bRCs of the carotenoidless mutant R. sphaeroides R-26 leads to a loss of photochemical activity and protein damage in the presence of oxygen. This effect is suppressed in wild-type strain 2.4.1 and also in R-26 when the... 

Fig. 3. Absorbance change due to quinone reduction in a reaction-center complex isolated from the carotenoidless mutant of Rb. sphaeroides. The sample contained reduced cytochrome and excess ascorbate as the secondary electron-donor system so that photooxidized P does not accumulate. The presence of excess ascorbate kept the oxidized cytochrome reduced, the net quinone reduction spectrum was obtained. Figure source Clayton (1980) Photosynthesis Physical Mechanisms and Chemical Patterns, p 95. Cambridge University Press.

Fig. 3.17 The S0 and T Raman spectra of undeuterated 15-c/s-spheroidene bound to the reaction center from Rba. sphaeroides 2.4.1 (wild type) and various deuterio derivatives incorporated into the reaction center from Rba. sphaeroides R26 (carotenoidless mutant).

Rba. sphaeroides R26 (carotenoidless mutant). The reaction center-bound D0 spheroidene exhibits unique spectral features in both the S0 and Ta states In the S0 state, it exhibits a key Raman line of the 15-ds configuration (at 1239 cm-1), which is a coupled mode of the C15-H and C15 -H in-plane bendings. The Raman profiles of other normal modes are similar to the case of all-trans-spheroi-... 

Fig. 18. (a) PPP-SD-CI calculations of n-bond orders in the So (open circles) and T (closed circles) states for a model of all-/ra/is-P-carotene(docosaundecaene). The Sg-state (open circles) and the Tpstate (closed circles) stretching force constants (k) determined for (b) all-/wns-spheroidene in n-hexane solution and (c) 15-cis Spheroidene bound to the RC of a carotenoidless mutant Fb. sphaeroides R26 are also shown. Double circles indicate those force constants assumed for both the Sq and the T states. 

A. Incorporation of Exogenous Carotenoids into Reaction Centers from Carotenoidless Mutants...237... 

Davidson Eand Cogdell RJ (1981) Reconstitution of carotenoids into the light-harvesting pigment-protein complex from the carotenoidless mutant of Rhodopseudomorms sphaeroides R-26. Biochim Biophys Acta 635 295-303... 

Theiler R, Suter F, Zuber H and Cogdell RJ (1984) Acomparison of the primary stmctures of the two B800-850-apoproteins from wild-type Rhodopseudomonas sphaeroides strain 2.4.1 and carotenoidless mutant strain R26.1. FEBS Lett 175 231-237... 

The biochemical architecture of photosynthetic bacteria is not as complex as that of green plants. For example, photosynthetic bacteria have only one photosystem, while green plants have two. The reaction center protein from several species of photosynthetic bacteria can be isolated from the photosynthetic membrane. Reaction centers from the species Rhodopseudomonas sphaeroides have been extensively studied. Although minor details will change from one species to another, the important features are nearly identical. The reaction center protein has a molecular weight of about 70,000 daltons. Within the reaction center protein extracted from the carotenoidless mutant strain R26 of the species R. sphaeroides, are found four molecules of bacteriochlorophyll a, two molecules of bacteriopheophytin a, one atom of nonheme iron, and, depending on the isolation procedure used, one or two molecules of ubiquinone. The absorption spectrum of the isolated reaction center has been well characterized. It is shown in Fig. 4. Based on in vitro absorption spectra, the bands at 870, 800, and 600 nm have been assigned to the bacteriochlorophyll a molecule. Bands at 760 and 530 nm have been attributed to the bacteriopheophytin a. 

Here we present experimental evidence that the monomeric bacteriochlorophyll is required for triplet energy transfer from the primary donor to the carotenoid in photosynthetic bacterial reaction centers. Our approach is to use sodium borohydride to extract the monomeric bacteriochlorophyll from the reaction centers of the carotenoidless mutant Rb. sphaeroides R26 [3, 4]. The borohydride treated reaction centers are then reconstituted with the carotenoid, spheroidene [5], and the ability of the reaction center complex to carry out the primary donor-to-carotenoid triplet transfer reaction was examined by transient optical spectroscopy. Steady state optical absorption and circular dichroism (CD) measurements demonstrate diat spheroidene reconstituted into borohydride-treated Rb, sphaeroides R26 reaction centers is bound in a single site, in the same environment and with the same structure as spheroidene reconstituted into native Rb. sphaeroides R26 reaction centers. It is shown herein that the primary donor-to-carotenoid triplet transfer reaction is inhibited in the absence of the accessory bacteriochlorophyll. 

Rhodospirillum rubrum G9, a carotenoidless mutant, was grown photosynthetically at 32 Cells were harvested in... 

Chromatophores and Bchl-protein complexes were prepared from the carotenoidless mutant of R. sphaeroides and the wild types of i . sphaeroides, Rhodospirillym rubrum, Rhodopseudomonas palustris, and Chromatiwn vinosum, according to the procedures reported previously (K. Sauer and L.A. Austin, 1978 H. Hayashi et al., 1982a). Materials were suspended in a Tris buffer containing thioglycolic acid. The resonance Raman spectra were... 

Bacterial reaction centres were isolated from the carotenoidless mutant R-26 of Rhodopseudomonas sphaeroides, cytochrome bcq complex from beef heart,cytochrome bf complex from lettuce and plastocyanin from parsley. 

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