15-Cis-carotenoids found in the reaction center of a green sulfur bacterium Chlorobium tepidum and in the Photosystem I reaction center of a cyanobacterium Synechococcus vulcanus

Carotenoids were extracted, at 4 °C in complete darkness and under nitrogen atmosphere, from the reaction center (RC) of a green-sulfur bacterium and the Photosystem (PS) I RC of a cyanobacterium; each extract was subjected to high-performance liquid chromatography (HPLC) using an apparatus equipped with a two-dimensional diode-array detector in order to spectroscopically identify cis–trans carotenoids while performing HPLC analysis. In the extract from the RC of Chlorobium tepidum, 15-cis and all-trans--carotenes as well as 13-cis-, 15-cis- and all- trans-chlorobactenes (in the order of elution) were identified, whereas in the extract from the PS I RC of Synechococcus vulcanus, 15-cis-, all-trans- and 9-cis--carotenes were found. Thus, the universal presence of 15- cis carotenoids in the 'iron sulfur-type' RCs has been shown in addition to the previous cases of the 'quinone-type' RCs.     

Crystallization of Photosystem I Complexes from the Thermophilic Cyanobacterium, Synechococcus vulcanus

PSI complexes were isolated from the thermophilic cyanobacterium,Synechococcus vulcanus, by mild detergent treatment of the thylakoidmembranes, purified by sucrose-density gradient centrifugation,and then crystallized. High resolution SDS-PAGE revealed thepresence of the product of the psaI gene in S. vulcanus PSIcomplexes and crystals. Crystals of the PSI complexes retainedall of the components of electron carriers and subunit polypeptides(including PsaX) known in cyanobacteria. (Received July 22, 1998; Accepted October 19, 1998)