Spirilloxanthin

Agalidis, I., T. Mattioli, and F. Reiss-Husson. 1999. Spirilloxanthin is released by detergent from Rubrivivax gelatinosus reaction center as an aggregate with unusual properties. Photosynth. Res. 62 314-2. 

Spirilloxanthin [34255-08-8] M 596.9, m 216-218 . Crystd from CHC /pet ether, acetone/pet ether, CgHg/pet ether or CgHg. Purified by chromatography on a column of CaCO3/Ca(OH)2 mixture or deactivated alumina. It has UV Xmax at 463, 493 and 528nm, EjJj 2680 (493nm), in pet ether (b 40-70°). [Polgar et al. Arch Biochem Biophys 5 243 7944]. Stored in the dark in an inert atmosphere, at -20°. 

Carotenes can be hydroxylated and otherwise modified in a number of ways.110/128-131 The structure of zeaxanthin, one of the resulting xanthophylls, is indicated in Fig. 22-5. Some other xanthophylls are shown in Eq. 22-10. Lutein resembles zeaxanthin, but the ring at one end of the chain has been isomerized by a shift in double bond position to the accompanying structure. The photosynthetic bacterium Rho-dospirillum rubrum has its own special carotenoid spirilloxanthin, which has the accompanying structure at both ends of the chain. 

In purified preparations of antenna complexes obtained from several phototrophic purple bacteria, mixtures of metabolically related carotenoids are usually found (Cogdell and Thomber, 1979). The sole reported exception to this rule seems to be a B880 complex of Rhodo spirillum mbmm in which only spirilloxanthin was detected, although Duysens (in Cogdell and Thomber, 1979, pp. 77) suggested that its uniform carotenoid composition could be due to the use of old bacterial cultures as the source of the... 

We are investigating further the nature of the carotenoids present in the bacterial photosynthetic complexes. In this report we shall present evidence showing that whereas the R. rubrum antenna contains a mixture of carotenoids the composition of which changes with the nutritional state of the culture, only spirilloxanthin and, in minor amounts, monodemethylated spirilloxanthin are found in association with the R. rubrum reaction center. The current progress of our work on the functional bases of the differences in carotenoid composition between the antenna and the reaction center shall also be presented. 

The carotenoid absorption band of each purified preparation of antenna complexes was similar, in shape and location, to that of the membranes from which that particular preparation was derived. Besides, the similitude was kept unchanged after organic solvent extraction of the preparations (not shown). Then, it seems that the incorporation of carotenoid pigments to the antenna complexes in vivo is a nonspecific process. The detection of spirilloxanthin as the sole carotenoid of previously analyzed antenna preparations of the same microorganism seems to be accidental and, as suggested by Duysens (in Cogdell and Thomber, 1979, pp. 77), probably due to the use of old, spirilloxanthin enriched cultures as the starting material for complex solubilization. 

UO. Cyts h and c BChl a or b Intracyloplasmic membrane Spirilloxanthin, okenone, (/3-carotene), spheroidene, rhodopin, lycopene, neurosporene... 

It is known from previous biochemical characterizations that LHl of Rs. rubrum, like the LB2 complexes just discussed, also consists of two types of polypeptides, a and p, containing 52 and 54 amino-acid residues, respectively. Each polypeptide has an a-helix spanning the membrane. Two conserved histidine residues (a-His29 and P-His37) have been implicated in the binding of BChl a, each ap-subunit being associated with 2 BChl-a molecules, as well as 1 carotenoid molecule, spirilloxanthin. 

Van Niel CB and Smith HC (1935) Studies on the pigments of the purple bacteria. I On spirilloxanthin, a component of the pigment complex of Spirillum rubrum. Arch Mikrobiol 6 219-229... 

The Rhodospirillaceae and Chromatiaceae have the spirilloxanthin or the okenone pathway depending on the genus or species. All of the Ectothiorhodospiraceae have the spirilloxanthin pathway. The isorenieratene, the y-and -carotene, and the diapocarotene pathways are found specifically in the Chlorobiaceae, Chloroflexaceae, and Heliobacteriaceae, respectively. Aerobic photosynthetic bacteria mostly have the spirilloxanthin pathway, further most of these species have unusual carotenoids including non-photosynthetic carotenoids, such as carotenoid sulfates and carotenoic acids, which have no photosynthetic functions. 

Spirilloxanthin pathway (normal spirilloxanthin, unusual spirilloxanthin, spheroidene, and carotenal pathways). 

Most of the aerobic photosynthetic bacteria so far desaibed have the spirilloxanthin pathway, further some also have unusual carotenoids as described below. 

Normal spirilloxanthin Unusual spirilloxanthin Spirilloxanthin Unusual-Spirillo Rhodospirillaceae, Chromatiaceae, Ectothiorhodospiraceae Rhodospirillaceae, Chromatiaceae, Ectothiorhodospiraceae 4... 

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